Recently I was tasked to share/branch a complex source tree in Visual SourceSafe 6.0 to do some changes with our project. For some reason, I found it very hard to do and I kept getting this error:

What the heck does "A project cannot be shared under a descendant" mean? After some testing, it turns out the reason for this error is because VSS attempts to add the folder you specified to itself. That is why this is a recursive error: you are adding a folder to the folder you are recursively scanning. I tried specifying a path (ie. $/ProjectA-Copied), but it refuses to recognize the full path and keeps wanting to add to itself ($/ProjectA/ProjectA-Copied). For the life of me, I just couldn't get VSS to share to another location.

After asking around some people, Paul (thanks!) told me that the problem is when you select Share on a project (aka folder) in VSS Explorer, you are selecting the destination project, not the source. Boy... great user experience isn't it?

Armed with this key piece of knowledge, I created my destination project, selected Share on the destination project, in the share dialog selected the source project, and finally was able to successfully share that source project to the destination project.

Also if you are branching after sharing and you have a project with lots of files, I recommend you use the Branch after share check box:

If you share without branching in one step, then you will have to manually go into the destination project and branch all the files individually. Nope, you cannot branch on the project level!

And finally, yes we're using Visual SourceSafe, yes I know it sucks, and finally (what I'm most happy about) yes we will be moving to Team Foundation Server and Visual Studio Team Suite!

你可以想象的出，一个库函数的异常信息不完整，对于他的用户来说，是多么不友好的事情。假设 MSDN 中 File.Open() 会抛出 IOException ，你的程序就很难想到很规矩的对 IOException 做了 catch ，然后提示用户检查相应位置的文件是否存在 / 被打开等。别指望 MSDN 的那些信息能够对终端用户有多大的帮助，太多不懂计算机的人在傻呆呆的握着鼠标了。再加上 MicroSoft 的提示信息本身就存在着“答非所问”，“莫名其妙”的事情，用户看到这些情况就更不知道怎么解决问题了。再加上自己的应用程序中会弹出一个个“蹩脚”的运行时错误的错误框，真的不是一个很如意的创作。

        但是，如果使用的是 Checked Exception ，这时候编译器会强迫你的外部接口的异常相当的完整，最起码可以做到比 MSDN 的异常类型齐整。

1.1 ． .NET Framework 1.1

   public StreamWriter(    string path  );

异常

1.2 JDK 1.4.2 :

public FileWriter(String fileName)  throws IOException

				Constructs a FileWriter object given a file name. 
		

Parameters:

fileName - String The system-dependent filename.

Throws:

IOException - if the named file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason

2 、解析

.NET 的 Excetpion 是 Unchecked 异常，客户端不要求去 Check 代码，但是 JAVA 的绝大部分 Checked 异常，它要求客户端的代码检测异常。

假设一个这样的场景，方法 OutMethod 调用 InnerMethod ，而内部方法 InnerMethod 抛出的异常 InnerException 。

对于 Java 的 CheckedException ，或者 OutMethod 去抛出 InnerException ，或者 OutMethod 捕捉 InnerException （然后做处理）。

再来观察一下 JDK 的 FileWriter 的异常声明，我没有详细测试其在各种可能出错情况下抛出的 IOException 的消息，但是其分类远远不如 .NET 的 StreamWriter 。假设 Java 想照抄 .NET 的 StreamWriter ，对于 Java 的使用者来说，无异于恶梦。外部的代码需要捕获如此多的异常消息（不捕捉就会在 OutMethod 抛出一大堆的异常，问题继续传播下去，这是 CheckException 的一个弱点）。也许正是出于这样的问题，所以此处 Java 接口的异常声明比较简单。

那么假设我是一个库设计者，正在用到了 IO 。如果我使用 .NET 进行开发，对于 IOException 来说，我是否有必要捕捉呢？捕捉的目的是为了“处理”，那么对于库设计者，显然这时候需要通知其“客户程序员”出错的原因，所以这里的库设计者的行为最好就是“不处理”。如果处理，那只能是“ catch 、再 throw ”。那么这样的处理显然是无意义的，因为原始异常已经足以提醒客户程序员出错的原因了。如果捕捉，那代码会特别的丑陋（直接 catch Exception 的行为是不可取的）。

CheckedException 的另外一个缺点就是“将 Exceotion 加入了 Interface 的规格声明“。假设 OutMethod 调用了 InnerMethod ，此时 InnerMethod 的设计者需要增加一个异常，那么会直接影响到 OutMethod 。当然这里的 InnerMethod 的设计者此时已经做了“修改接口声明“的行为。

   随后待续...... 

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： jinfeng_W...@msn.com - 查找此作者的帖子 
日期：19 Jan 2006 17:56:57 -0800
当地时间：2006年1月20日(星期五) 上午9时56分 
主题：the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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hi, I have a question about the difference between
SqlConnection.IDisposable.Dispose()  and  SqlConnection.Dispose(). Both
 of them realize the function of releasing the connection to the
ConnectionPool?  Do they have the same effection source code?  If they
are different, who can tell me the differences? If they are same, why
MS gives the SqlConnection.IDisposable.Dispose, but  only
SqlConnection.Dispose() method?

In the MSDN, there are following description about the
SqlConnection.IDisposable.Dispose Method:
  "This member supports the .NET Framework infrastructure and is not
intended to be used directly from your code."  what's the meaning of
it?

If the user has called the SqlConnection.IDisposable.Dispose() in the
client application, what probem results in?  and if there are some
problem becomes, then why did MS give us such a method?

in the same, who can tell me the using of
"SqlConnection.ICloneable.Clone ",
"SqlConnection.IDbConnection.BeginTransaction" and
"SqlConnection.IDbConnection.CreateCommand"?

Anybody can help me to solve my question? thanks a lot.

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   2. Cor Ligthert [MVP]
 1月20日 下午3时10分   显示选项

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发件人： "Cor Ligthert [MVP]" <notmyfirstn...@planet.nl> - 查找此作者的帖子 
日期：Fri, 20 Jan 2006 08:10:00 +0100
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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JinFeng,

Both of them are removing the connectionstring from the connectionobject.
They both have nothing to do direct with the ConnectionPool, although you
should close a connection either by close or dispose to let the
ConnectionPool do its job.

Every Interface can be used to get its members (in the implementing
contract) from the implementing class. Therefore it is an interface. A good
programmer start the name of his interfaces all with a capital I.

I hope that this gives an idea

Cor

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   3. jinfeng_Wang@msn.com
 1月20日 下午5时52分   显示选项

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日期：20 Jan 2006 01:52:12 -0800
当地时间：2006年1月20日(星期五) 下午5时52分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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hello, Cor . thanks for you answer. but it's not what i want.

please read the following URL and look at the left frame:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpre...

there are two methods in the SQLConnection:
 "Dispose"  and  "SqlConnection.IDisposable.Dispose" Method.

and in MSDN , the description about the
"SqlConnection.IDisposable.Dispose" is:  "This member supports the .NET
Framework infrastructure and is not intended to be used directly from
your code".
can you help to tell me, what's the meaning of the above setence? MS
advice me that i should not call the
"SqlConnection.IDisposable.Dispose", yeah?

if there is a client code, like this  (copied from  MSDN, and i have
modified it):
public void ReadMyData()
{
    String      myConnString = "Persist Security Info=False;User
ID=sa;Initial Catalog=Northwind;Data Source=DTK-S-SVR;User
ID=sa;Pwd=sa";
   string mySelectQuery = "SELECT OrderID, CustomerID FROM Orders";
   SqlConnection myConnection = new SqlConnection(myConnString);
   SqlCommand myCommand = new SqlCommand(mySelectQuery,myConnection);
   myConnection.Open();
   SqlDataReader myReader;
   myReader = myCommand.ExecuteReader();
   while (myReader.Read())
      {
        Console.WriteLine(myReader.GetInt32(0) + ", " +
myReader.GetString(1));
     }
    myReader.Close();

     //myConnection.Close();  // old source code.
     IDisposable disposable =myConnection as IDisposable;   // new
source code.
     disposable.Dispose();   // new source code.

}

will it cause some problem when cast the myConnection  to IDisposable
and call  disposable.Dispose() ?
Does the "new souce code" have the same effect as the "old source code"
??
if they are, why MS implements the method of "IDisposable.Disp­ose()"
explicity. I means: there is only the SqlConnection.Dispose() method.

if there is no problem here, then can you why MS said that "This member
supports the .NET Framework infrastructure and is not intended to be
used directly from your code."??
if there is some problem, then why MS does not make the methods of
SqlConnection.IDisposable.Disp­­ose() and SqlConnection.Dispose()
shared the same source code? and why MS tell us that there exists a
"SqlConnection.IDisposable.Disp­­ose()" method, but warn us not to
call it??

in the same, how about the "SqlConnection.ICloneable.Clone ",
"SqlConnection.IDbConnection.BeginTransaction" and
"SqlConnection.IDbConnection.CreateCommand"?

i do not whether you have understand my question for my poor english
and expression.
can you help me? anyway, thanks to all of you.

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   4. Cor Ligthert [MVP]
 1月20日 下午6时29分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "Cor Ligthert [MVP]" <notmyfirstn...@planet.nl> - 查找此作者的帖子 
日期：Fri, 20 Jan 2006 11:29:36 +0100
当地时间：2006年1月20日(星期五) 下午6时29分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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JinFeng,

Both Frans and me are not first language English speakers (AFAIK is Frans
born where the native language is Fries and I where it is Dutch). In my
opinion should you never excuse you for your English in these newsgroups.
Almost everybody, no matter how good he can speak a language, will make
errors in email messages (even in his own). I assume that you are using the
English version of Visual Studio so that tells enough.

I thought that the protected dispose is used by component (don't mix this up
with the rest from what I write about component). If you open a form or a
component (by the designer), than you see the implementation of IDisposable
direct. That part is used to do the most of the disposing.

Nice pages about Idisposable are these new ones

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpre...

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpre...

As I said, be aware that if you use a form or a component the code is
already in the designer created part.

However as long discussions has be done in this newsgroup. Disposing and
Closing have the same effect on the connection pool.

I hope this gives some information.

Cor

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   5. Frans Bouma [C# MVP]
 1月20日 下午4时22分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "Frans Bouma [C# MVP]" <perseus.usenetNOS...@xs4all.nl> - 查找此作者的帖子 
日期：Fri, 20 Jan 2006 00:22:50 -0800
当地时间：2006年1月20日(星期五) 下午4时22分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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- 隐藏被引用文字 -
- 显示引用的文字 -

jinfeng_W...@msn.com wrote:
> hi, I have a question about the difference between
> SqlConnection.IDisposable.Dispose()  and  SqlConnection.Dispose().
> Both  of them realize the function of releasing the connection to the
> ConnectionPool?  Do they have the same effection source code?  If they
> are different, who can tell me the differences? If they are same, why
> MS gives the SqlConnection.IDisposable.Dispose, but  only
> SqlConnection.Dispose() method?

> In the MSDN, there are following description about the
> SqlConnection.IDisposable.Dispose Method:
>   "This member supports the .NET Framework infrastructure and is not
> intended to be used directly from your code."  what's the meaning of
> it?

> If the user has called the SqlConnection.IDisposable.Dispose() in the
> client application, what probem results in?  and if there are some
> problem becomes, then why did MS give us such a method?

> in the same, who can tell me the using of
> "SqlConnection.ICloneable.Clone ",
> "SqlConnection.IDbConnection.BeginTransaction" and
> "SqlConnection.IDbConnection.CreateCommand"?

> Anybody can help me to solve my question? thanks a lot.

        what does 'SqlConnection.IDisposable.Dispose' mean? 'IDisposable'
isn't a property or something of SqlConnection. 'Dispose()' is a method
in Component, the base class of SqlConnection. SqlConnection overrides
Dispose(true), which is called from Dispose(), and therefore whatever
Dispose() you call, it doesnt matter.

                FB

--
------------------------------------------------------------------------
Get LLBLGen Pro, productive O/R mapping for .NET: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

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   6. jinfeng_Wang@msn.com
 1月20日 下午5时55分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "jinfeng_W...@msn.com" <jinfeng_W...@msn.com> - 查找此作者的帖子 
日期：20 Jan 2006 01:55:46 -0800
当地时间：2006年1月20日(星期五) 下午5时55分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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FB, i know that 'IDisposable'  is not one property of the
SQLConnection. please read my answer to Cor.
'SqlConnection.IDisposable.Dispose'  is copied from MSDN.    :-)
I think it means that SQLConnection has implemnt the Dispose() method
of the IDisposable explicity.

I want to know the difference between the two method of
SqlConnection.IDisposable.Disp­­ose() and SqlConnection.Dispose().

Thanks to you!!! thanks!

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   7. Frans Bouma [C# MVP]
 1月21日 下午6时54分   显示选项

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发件人： "Frans Bouma [C# MVP]" <perseus.usenetNOS...@xs4all.nl> - 查找此作者的帖子 
日期：Sat, 21 Jan 2006 02:54:24 -0800
当地时间：2006年1月21日(星期六) 下午6时54分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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jinfeng_W...@msn.com wrote:
> FB, i know that 'IDisposable'  is not one property of the
> SQLConnection. please read my answer to Cor.
> 'SqlConnection.IDisposable.Dispose'  is copied from MSDN.    :-)
> I think it means that SQLConnection has implemnt the Dispose() method
> of the IDisposable explicity.

        I thought that it meant that, but checking SqlConnection in reflector
I couldn't find IDisposable explicit implementations :D Hence my
question :)

> I want to know the difference between the two method of
> SqlConnection.IDisposable.Disp­­ose() and SqlConnection.Dispose().

        I have no idea.

                FB

--
------------------------------------------------------------------------
Get LLBLGen Pro, productive O/R mapping for .NET: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

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   8. jinfeng_Wang@msn.com
 1月23日 上午9时17分   显示选项

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日期：22 Jan 2006 17:17:00 -0800
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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:-)

copied from Reflector:

System.Data.SqlClient.SqlConnection.System.Data.IDbConnection.BeginTransact­ion()
: IDbTransaction
IDbTransaction IDbConnection.BeginTransaction()
{
      return this.BeginTransaction();

}

I think that the disposable is same as here .
but, but  why MS does such a foolish action :-(

this folliwing is copied from MSDN  in the
SqlConnection.IDbConnection.BeginTransaction Method ():
"This member supports the .NET Framework infrastructure and is not
intended to be used directly from your code."
faint to death. ~

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   9. William (Bill) Vaughn
 1月22日 上午2时55分   显示选项

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发件人： "William \(Bill\) Vaughn" <billvaRemoveT...@nwlink.com> - 查找此作者的帖子 
日期：Sat, 21 Jan 2006 10:55:46 -0800
当地时间：2006年1月22日(星期日) 上午2时55分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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Ok... if you're that curious, use Reflector to walk through the .Net
Framework code to see what it does. You must have a lot more time on your
hands that we do.

Frankly, it does not matter what they do. You don't need to call
them--either of them. As long as you use Close on the Connection you're
fine. Sure, you can call Dispose if you want to, but it won't help the
problem you're trying to solve.

--
____________________________________
William (Bill) Vaughn
Author, Mentor, Consultant
Microsoft MVP
INETA Speaker
www.betav.com/blog/billva
www.betav.com
Please reply only to the newsgroup so that others can benefit.
This posting is provided "AS IS" with no warranties, and confers no rights.
__________________________________

"Frans Bouma [C# MVP]" <perseus.usenetNOS...@xs4all.nl> wrote in message
news:xn0ehgc512v14b001@news.microsoft.com...

- 隐藏被引用文字 -
- 显示引用的文字 -

> jinfeng_W...@msn.com wrote:

>> hi, I have a question about the difference between
>> SqlConnection.IDisposable.Dispose()  and  SqlConnection.Dispose().
>> Both  of them realize the function of releasing the connection to the
>> ConnectionPool?  Do they have the same effection source code?  If they
>> are different, who can tell me the differences? If they are same, why
>> MS gives the SqlConnection.IDisposable.Dispose, but  only
>> SqlConnection.Dispose() method?

>> In the MSDN, there are following description about the
>> SqlConnection.IDisposable.Dispose Method:
>>   "This member supports the .NET Framework infrastructure and is not
>> intended to be used directly from your code."  what's the meaning of
>> it?

>> If the user has called the SqlConnection.IDisposable.Dispose() in the
>> client application, what probem results in?  and if there are some
>> problem becomes, then why did MS give us such a method?

>> in the same, who can tell me the using of
>> "SqlConnection.ICloneable.Clone ",
>> "SqlConnection.IDbConnection.BeginTransaction" and
>> "SqlConnection.IDbConnection.CreateCommand"?

>> Anybody can help me to solve my question? thanks a lot.

> what does 'SqlConnection.IDisposable.Dispose' mean? 'IDisposable'
> isn't a property or something of SqlConnection. 'Dispose()' is a method
> in Component, the base class of SqlConnection. SqlConnection overrides
> Dispose(true), which is called from Dispose(), and therefore whatever
> Dispose() you call, it doesnt matter.

> FB

> --
> ------------------------------------------------------------------------
> Get LLBLGen Pro, productive O/R mapping for .NET: http://www.llblgen.com
> My .NET blog: http://weblogs.asp.net/fbouma
> Microsoft MVP (C#)
> ------------------------------------------------------------------------

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   10. Frans Bouma [C# MVP]
 1月22日 下午6时52分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "Frans Bouma [C# MVP]" <perseus.usenetNOS...@xs4all.nl> - 查找此作者的帖子 
日期：Sun, 22 Jan 2006 02:52:11 -0800
当地时间：2006年1月22日(星期日) 下午6时52分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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William (Bill) Vaughn wrote:
> Ok... if you're that curious, use Reflector to walk through the .Net
> Framework code to see what it does. You must have a lot more time on
> your hands that we do.

> Frankly, it does not matter what they do. You don't need to call
> them--either of them. As long as you use Close on the Connection
> you're fine. Sure, you can call Dispose if you want to, but it won't
> help the problem you're trying to solve.

        On a side note: not all ADO.NET providers' connection objects can
live without a Dispose call. For example the Firebird .NET provider and
the ODP.NET providers do need a call to Dispose to properly clean up.
(especially firebird, for cleaning up on the server side!).

        FB, who still couldn't find an explicit IDisposable implementation on
SqlConnection...

--
------------------------------------------------------------------------
Get LLBLGen Pro, productive O/R mapping for .NET: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
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------------------------------------------------------------------------

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11. jinfeng_Wang@msn.com
 1月23日 上午8时55分   显示选项

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日期：22 Jan 2006 16:55:26 -0800
当地时间：2006年1月23日(星期一) 上午8时55分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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thanks all of you.

If i was just a client programmer, i think all the information from you
and MSDN is enough.
but,...  now i am trying  to develop one new .NET Data Provider for own
database.
so i want  to know what has happened in SQL .NET Data Provider.
it give me a dozens of puzzling interface.
here is "SqlConnection.IDisposable.Disp­­ose() " and
"SqlConnection.Dispose()".

In fact, the SQLConnection is inherited from Compnent, which has
implemented the IDisposable.
This is very like the question of "deadly diamond", that one Class
inherits one Interface from TWO path.
             IDisposable
              /                \
              |                 |
Component       IDBConnection
              |                 |
              \                /
            SQLConnection

if there is no difference between the
SqlConnection.IDisposable.Disp­­ose() and SqlConnection.Dispose(),
then MS has no need to implement the
SqlConnection.IDisposable.Disp­­ose() explicitly. But, it has done
it, that means there are some differences between them. What's that?
MSDN has not told us, it just warn us not to call  the
SqlConnection.IDisposable.Disp­­ose() in the client program.    :(

In the  Oracle® Data Provider for .NET,
     public sealed class OracleConnection : Component, IDbConnection,
ICloneable
but, OracleConnection has not implement the
IDbConnection.IDisposable.Disposable() explicity.

MS, :-(

 14. Frans Bouma [C# MVP]
 1月23日 下午5时54分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "Frans Bouma [C# MVP]" <perseus.usenetNOS...@xs4all.nl> - 查找此作者的帖子 
日期：Mon, 23 Jan 2006 01:54:56 -0800
当地时间：2006年1月23日(星期一) 下午5时54分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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jinfeng_W...@msn.com wrote:
> If i was just a client programmer, i think all the information from
> you and MSDN is enough.
> but,...  now i am trying  to develop one new .NET Data Provider for
> own database.

        there are guidelines for that if I'm not mistaken. And I think you
should relax a little. I work with a lot of ADO.NET providers and none
of them works the same as the others. So 'what should be done' is what
you think is the easiest for your users :).

        So, 'Close()' should clean up, and for example connection.Dispose()
should also dispose commands, parameters etc.

        In general derive a class from DbConnection, and override the specific
methods to add your own code.

> so i want  to know what has happened in SQL .NET Data Provider.
> it give me a dozens of puzzling interface.
> here is "SqlConnection.IDisposable.Disp­­ose() " and
> "SqlConnection.Dispose()".

        Have you looked into the code with reflector ? I think you should do
that. :)

- 隐藏被引用文字 -
- 显示引用的文字 -

> In fact, the SQLConnection is inherited from Compnent, which has
> implemented the IDisposable.
> This is very like the question of "deadly diamond", that one Class
> inherits one Interface from TWO path.
>              IDisposable
>               /                \
>               |                 |
> Component       IDBConnection
>               |                 |
>               \                /
>             SQLConnection

> if there is no difference between the
> SqlConnection.IDisposable.Disp­­ose() and SqlConnection.Dispose(),
> then MS has no need to implement the
> SqlConnection.IDisposable.Disp­­ose() explicitly. But, it has done
> it, that means there are some differences between them. What's that?
> MSDN has not told us, it just warn us not to call  the
> SqlConnection.IDisposable.Disp­­ose() in the client program.    :(

        I looked up the page, and I can only get to that page through the
index. So I think it's a mistake in the MSDN. As said by others in this
thread, look at the code through reflector first, then come back here
with questions.

        Also, inherited interfaces are simply type definitions, not
implementations. So 1 routine can serve the Dispose() method of
multiple interfaces.

> In the  Oracle® Data Provider for .NET,
>      public sealed class OracleConnection : Component, IDbConnection,
> ICloneable
> but, OracleConnection has not implement the
> IDbConnection.IDisposable.Disposable() explicity.

> MS, :-(

        Neither has sqlconnection!!! Look into the code! Just because it's an
error in the MSDN doesn't mean it's true. Why do you ignore what we
said and keep believing an errorous page in the msdn?

                FB

--
------------------------------------------------------------------------
Get LLBLGen Pro, productive O/R mapping for .NET: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

回复
             
     

 
   15. jinfeng_Wang@msn.com
 1月23日 下午10时15分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "jinfeng_W...@msn.com" <jinfeng_W...@msn.com> - 查找此作者的帖子 
日期：23 Jan 2006 06:15:59 -0800
当地时间：2006年1月23日(星期一) 下午10时15分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
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:-)

MSDN Error？
why the MS make such an Error .
I have said that  now i am developing one .NET Data Provider for my own
database, so i should know the everything what have happened in the SQL
.NET  Data Provider, and learning something from the MS's code.

now i have realized why MS  give us such a SQL .NET  Data Provider.
wait a minute, and i  will write it clearly.

回复
             
     

 
   16. jinfeng_Wang@msn.com
 1月23日 下午11时10分   显示选项

新闻论坛：microsoft.public.dotnet.framework.adonet
发件人： "jinfeng_W...@msn.com" <jinfeng_W...@msn.com> - 查找此作者的帖子 
日期：23 Jan 2006 07:10:37 -0800
当地时间：2006年1月23日(星期一) 下午11时10分 
主题：Re: the difference between SqlConnection.IDisposable.Disp­ose() and SqlConnection.Dispose()
回复 | 答复作者 | 转发 | 打印 | 显示个别帖子 | 显示原始邮件 | 删除 | 报告滥用行为 

firstly, let's take a look at the following code.

///--------------
        public interface myInterface
        {
                Object getobject();
        }

        public class MyImplement : myInterface
        {
                public String getobject()    //override.
                {
                        return "str";
                }
        }///---------------
the code above can not be compiled, the compiler will have give us an
error.  Because the method of MyImplement.getobject() has a wrong
return type, which is "String", but the method of
MyInterface.getobject() declared that the return type is "Object:. Here
the compiler take the "return type" into the "override" compile
progregess. If MyImplement.getobject() returns "String",  this is not
the implementation of MyInterface.getobject().

now let's take a look at another code.
///---------------
        public class AnotherImplement
        {
                public object getobject()
                {
                        return new object();
                }

                public string getobject()  //overload
                {
                        return new string("");
                }

        }
///---------------
Here I want to overload the method of "getobject()", but the compiler
give us an error. Here the compiler DOES NOT take the "return type"
into the "overload" compile progregess (DIFFERENCE WITH THE OVERRIDE).

Now let's go back to the IDBConnection and SQLConnection.
In the interface of IDbConnection, it declares one method of
"createcomand".
///----------
IDbConnection {
    ....
    IDbCommand CreateCommand();
   ....

}

///----------
When design the interface of IDBConnection, the designer does not
what's kind of "Command" will be returned, for example
"SQLCommand","OracleCommand". so in the IDbConnection.CreateCommand(),
it only return an interface of "IDbCommand".

Now we are design the SQLConnection which implements the interface of
"IDbConnection". if in the SQLConnection, it only write :
///---------
  SQLConnection:IDbConnection {
   ....
      SQLCommand  CreateCommand() {
              ........
      }
   ....
 }
///---------
the compiler will give us an error, because  the "return type" is
SQLCommand, but not IDbCommand(defined in the IDbConnection). THE
COMPILER TAKE THE RETURN TYPE INTO THE COMPILE PROGRESS. so we must
give another definition of "IDbConnection.CreateCommand()".

if we write the code as follows:
///---------
  SQLConnection:IDbConnection {
   ....
      SQLCommand  CreateCommand() {
              ........
      }

      IDBCommand CreateCommand() {
              .......
     }
   ....
 }
///---------
The compiler will give us an error. THE COMPILER DOES NOT TAKE THE
RETURN TYPE INTO THE COMPILE PROGRESS.

so the SQLConnection have to implement  the
IDbConncection.CreateCommand explicyly.
///--------
   SQLConnection:IDbConnection {
   ....
      SQLCommand  CreateCommand() {
              ........
      }

      IDBCommand  IDbConnection.CreateCommand() {
              return this.CreateCommand();
     }
   ....
 }
///---------
The above is the  SQLConnection.

============BUT============
The MSDN told us the "we should call the
SQLConnection.IDbConnection.CreateCommand() in the client program".
that is, "we should use the SQLConnection.CreateCommand() in the client
program."
THIS will result a foolish result. In the client pogram, we will write
such a code:
///------------
   void doSomething() {
         SqlConnection  conn = new SqlConnection(connectionString);
         SqlCommand command = conn.CreateCommand();
                           //  We MUST have call
SqlConnection.CreateCommand(),
                           //  not
SqlConnection.IDbConnection.CreateCommand(),
                           //  which is suggested by MSDN.
   }
///------------
The above client code has violated the programming rule: "PROGRAMMING
TO INTERFACE".
According to the MSDN, we can not "PROGRAM TO IDbCommand".
The action of  "SqlConnection.CreateCommand()"  is difference with  the
action of"IDbConnection.CreeateCommand()".

Now if i want to shift to the Oracle database.   All of the client code
must be modified, because the above is "PROGRAM TO SqlCommand".  :-(
What a foolish ADO.NET FrameWork.

I am a java programmer. If i design the SQLConnection, i will give a
such a implemention:
///--------
   SQLConnection:IDbConnection {
   ....
      IDBCommand  CreateCommand() {
              ........
      }

      SqlCommand  CreateSqlCommand() {
              ........
     }
   ....
 }
///---------
If the client programmer want to "PROGRAM TO SqlCommand",  he will call
the method of SqlConnection.CreateSqlCommand().  If the client
programmer want to "PROGRAMM TO IDbConnection", he will call the
SqlConnection.CreateCommand(). Now The action of
"SqlConnection.CreateCommand()"  is same as   the action
of"IDbConnection.CreeateCommand()".
Because the client code is "PROGRAM TO IDbCommand", so if the client
program shifts to Oracle database, the client code will not have to
modify all the code.

回复
 

After reading a post on the C# newsgroup asking for a EBCDIC to ASCII converter, and seeing one solution, I decided to write my own implementation. This page describes the implementation and its limitations, and a bit about EBCDIC itself.

EBCDIC

Unfortunately it appears to be fairly tricky to get hold of many concrete specifications of EBCDIC. This is what I've managed to glean from various websites:

• Introduced by IBM, EBCDIC is an encoding mostly used on mainframes.
• Like "OEM", EBCDIC isn't a single character encoding: there are many EBCDIC encodings, suited to different cultures.
• It is primarily a single-byte encoding, ie each character is encoded as a single byte. However, there are two characters, "shift out" and "shift in" (0x0e and 0x0f respectively) which are used to change between this an a double-byte character set (DBCS). As far as I can tell, a single EBCDIC encoding doesn't specify which DBCS is to be used - in other words, you really need even more information before you can tell what's going on. Presumably the DBCS in question can't have any pairs beginning with byte 0x0f, as otherwise it would be confused with the "shift in" flag.

If you have any more information, particularly about the DBCS aspect, please mail me at skeet@pobox.com.

My EBCDIC Encoding implementation

I managed to get hold of details of 47 EBCDIC encodings from http://std.dkuug.dk/i18n/charmaps/. To be honest, I don't really know what DKUUG is, so I'm really just hoping that the maps are accurate - they seem to be quite reasonable though. Each encoding has a name and several have aliases, although I currently ignore this aliasing.

My implementation consists of three projects, described below, of which only the middle one is of any interest to most people.

A character map reader

This simply finds all of the files whose names begin with "EBCDIC-" in the current directory, reads them all in (warning of any oddities in the encoding, such as any non-zero byte having two distinct meanings) and writes a resource file out, ebcdic.dat. This is a console applicion built from a single C# source file.

An encoding library

This is a library built from two C# source files and the ebcdic.dat file generated by the reader. This library is all most users will need. More details are provided below.

A test program

This is a console application built from a single C# source file and requiring the library described above. Currently it just displays the encoded version of "hello" and then decodes it.

Using The Encoding Library

The encoding library is very simple to use, as the encoding class (JonSkeet.Ebcdic.EbcdicEncoding) is a subclass of the standard .NET System.Text.Encoding class. To obtain an instance of the appropriate encoding, use EbcdicEncoding.GetEncoding (String) passing it the name of the encoding you wish to use (eg EBCDIC-US). You can find out the list of names of available encodings using the EbcdicEncoding.AllNames property, which returns the names as an array of strings.

Once you have obtained an EbcdicEncoding instance, use it like any other Encoding: call GetString, GetBytes etc. The encoding does not save any state between requests, and can safely be used by many threads simultaneously. There is no need (or indeed facility) to release encoding resources when it is no longer needed. All encodings are created on the first use of the EbcdicEncoding class, and maintained until the application domain is unloaded.

Sample Code

The following is a sample program to convert a file from EBCDIC-US to ASCII. It should be easy to see how to modify it to convert the other way, or to use a different encoding (eg from EBCDIC-UK, or to UTF-8).

using System;
using System.IO;
using System.Text;
using JonSkeet.Ebcdic;

public class ConvertFile
{
    public static void Main(string[] args)
    {
        if (args.Length != 2)
        {
            Console.WriteLine 
                ("Usage: ConvertFile <ebcdic file (input)> <ascii file (output)>");
            return;
        }
        
        string inputFile = args[0];
        string outputFile = args[1];

        Encoding inputEncoding = EbcdicEncoding.GetEncoding ("EBCDIC-US");
        Encoding outputEncoding = Encoding.ASCII;
        
        try
        {
            // Create the reader and writer with appropriate encodings.
            using (StreamReader inputReader = 
                      new StreamReader (inputFile, inputEncoding))
            {
                using (StreamWriter outputWriter = 
                           new StreamWriter (outputFile, false, outputEncoding))
                {
                    // Create an 8K-char buffer
                    char[] buffer = new char[8192];
                    int len=0;
                    
                    // Repeatedly read into the buffer and then write it out
                    // until the reader has been exhausted.
                    while ( (len=inputReader.Read (buffer, 0, buffer.Length)) > 0)
                    {
                        outputWriter.Write (buffer, 0, len);
                    }
                }
            }
        }
        // Not much in the way of error handling here - you may well want
        // to do better handling yourself!
        catch (IOException e)
        {
            Console.WriteLine ("Exception during processing: {0}", e.Message);
        }
    }
}    

Limitations

Due to the lack of available information about the DBCS aspect of EBCDIC, this encoding class makes no effort whatsoever to simulate proper shifting. Shift out and shift in are merely encoded/decoded to/from their equivalent Unicode characters, and bytes between them are treated as if the shift had not taken place. (This means that a decoded byte array is always a string of the same length as the byte array, and vice versa).

Any byte not recognised to be from the specific encoding being used is decoded to the question mark character, '?'. Any character not recognised to be in the set of characters encoded by the specific encoding being used is encoded to the byte representing the question mark character, or to byte zero if the question mark character is not in the character set either.

The library doesn't currently have a strong-name, so can't be placed in the GAC. You may, however, download the source and modify

Licence

This was just an interesting half-day project. I have no desire to make any money out of this code whatsoever, but I hope it's interesting and useful to others. So, feel free to use it. If you have any questions about it, or just find it useful and wish to let me know, please mail me at skeet@pobox.com. You may use this code in commercial projects, either in binary or source form. You may change the namespace and the class names to suit your company, and modify the code if you wish. I'd rather you didn't try to pass it off as your own work, and specifically you may not sell just this code - at least not without asking me first. I make no claims whatsoever about this code - it comes with no warranty, not even the implied warranty of fitness for purpose, so don't sue me if it breaks something. (Mail me instead, so we can try to stop it from happening again.)

Downloads

• Source code and VS.NET 2003 solution (zip file, 20K, also contains instructions for building from the command line.
• Debug version of the encoding library as built by VS.NET 2003 (zip file, 11K, contains the DLL and PDB files)
• Release version of the encoding library as built by VS.NET 2003 (zip file, 6K, contains just the DLL)

History

• August 31st 2003, v1.0.0.1 - no in-code changes, just made the XML documentation build correctly.
• August 28th 2003, v1.0.0.1 - slight tweaking to remove unnecessary (and probably counterproductive) efficiency measure. No functional changes.
• May 21st 2003, v1.0.0.0 - initial implementation.