Database Connection

[=?Utf-8?B?VHJlY2l1cw==?=]

Hello, Newsgroupians:

Recently I asked a question regarding database connections and how to
properly close the connection upon the object going out of scope. After much
research, I've come up with a solution -- I believe -- should work, but
doesn't work. I'd like to ask for your continued feedback.

I create a class that wraps the DBConnection. Here's a small sample...

class CDB : IDispose
{
...
protected System.Data.Common.DBConnection m_conn = null;

public CDB()
{
...
this.m_conn.Open();
System.GC.SuppressFinalize(this.m_conn); // IMPORTANT
}
public Disconnect()
{
if (this.m_conn.State == System.Data.ConnectionState.Open)
{
this.m_conn.Close();
}
}
...
}

Now for my Dispose() and destructor, which is a Finalize() method, I have
the following...

~CDB()
{
this.Disconnect();
this.m_conn.Dispose();
}

public void Dispose()
{
this.Disconnect();
this.m_conn.Dispose();
System.GC.SuppressFinalize(this);
}
Now, when I create an instance of my wrapper, it can connect and perform
queries to the specified database. However, when the object goes out of
scope, it calls the destructor. In the destructor, it calls Disconnect(),
where I get an error on the line that is "this.m_conn.Close()" stating the
handle is not initialized, but I told the garbage collector to NOT call
Finalize() on the this.m_conn. I told it not to do this in the constructor
of my wrapped object. So why is the m_conn being GC when I told it not to?

Thank you all for your continued support and patience.
Trecius

[Jon Skeet [C# MVP]]

Trecius <Tr*****@discussions.microsoft.comwrote:

Recently I asked a question regarding database connections and how to
properly close the connection upon the object going out of scope. After much
research, I've come up with a solution -- I believe -- should work, but
doesn't work. I'd like to ask for your continued feedback.

One reason it shouldn't work is your claim here:

Now, when I create an instance of my wrapper, it can connect and perform
queries to the specified database. However, when the object goes out of
scope, it calls the destructor.

An object doesn't go out of scope: a variable does. That, in itself,
won't cause the finalizer to be called. The finalizer will be called
*some point* after the object is no longer referenced.

As to the rest of your post, I'd be interested in seeing a short but
complete example demonstrating the problem. I can't say I've ever seen
SuppressFinalize being called on anything other than "this" - it seems
like a bad idea to me.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[=?Utf-8?B?UGV0ZXIgQnJvbWJlcmcgW0MjIE1WUF0=?=]

This code is "overkill". All you need to do is make a call to Close or
Dispose on your connection instance as soon as you are finished using it, and
allow it to go back to the ADO.NET connection pool. Forget about all the
finalizer / destructor stuff.
Peter

--
Recursion: see Recursion
site: http://www.eggheadcafe.com
unBlog: http://petesbloggerama.blogspot.com
BlogMetaFinder: http://www.blogmetafinder.com

"Trecius" wrote:

Hello, Newsgroupians:

Recently I asked a question regarding database connections and how to
properly close the connection upon the object going out of scope. After much
research, I've come up with a solution -- I believe -- should work, but
doesn't work. I'd like to ask for your continued feedback.

I create a class that wraps the DBConnection. Here's a small sample...

class CDB : IDispose
{
...
protected System.Data.Common.DBConnection m_conn = null;

public CDB()
{
...
this.m_conn.Open();
System.GC.SuppressFinalize(this.m_conn); // IMPORTANT
}
public Disconnect()
{
if (this.m_conn.State == System.Data.ConnectionState.Open)
{
this.m_conn.Close();
}
}
...
}

Now for my Dispose() and destructor, which is a Finalize() method, I have
the following...

~CDB()
{
this.Disconnect();
this.m_conn.Dispose();
}

public void Dispose()
{
this.Disconnect();
this.m_conn.Dispose();
System.GC.SuppressFinalize(this);
}
Now, when I create an instance of my wrapper, it can connect and perform
queries to the specified database. However, when the object goes out of
scope, it calls the destructor. In the destructor, it calls Disconnect(),
where I get an error on the line that is "this.m_conn.Close()" stating the
handle is not initialized, but I told the garbage collector to NOT call
Finalize() on the this.m_conn. I told it not to do this in the constructor
of my wrapped object. So why is the m_conn being GC when I told it not to?

Thank you all for your continued support and patience.
Trecius

[Alvin Bruney [MVP]]

Why not use the MS DAAB? It already works out all that stuff properly.

--
Regards,
Alvin Bruney
------------------------------------------------------
Shameless author plug
Excel Services for .NET - MS Press
Professional VSTO 2005 - Wrox/Wiley
OWC Black Book www.lulu.com/owc

"Peter Bromberg [C# MVP]" <pb*******@yahoo.yohohhoandabottleofrum.comwrote
in message news:F2**********************************@microsof t.com...

This code is "overkill". All you need to do is make a call to Close or
Dispose on your connection instance as soon as you are finished using it,
and
allow it to go back to the ADO.NET connection pool. Forget about all the
finalizer / destructor stuff.
Peter

--
Recursion: see Recursion
site: http://www.eggheadcafe.com
unBlog: http://petesbloggerama.blogspot.com
BlogMetaFinder: http://www.blogmetafinder.com

"Trecius" wrote:

>Hello, Newsgroupians:

Recently I asked a question regarding database connections and how to
properly close the connection upon the object going out of scope. After
much
research, I've come up with a solution -- I believe -- should work, but
doesn't work. I'd like to ask for your continued feedback.

I create a class that wraps the DBConnection. Here's a small sample...

class CDB : IDispose
{
...
protected System.Data.Common.DBConnection m_conn = null;

public CDB()
{
...
this.m_conn.Open();
System.GC.SuppressFinalize(this.m_conn); // IMPORTANT
}
public Disconnect()
{
if (this.m_conn.State == System.Data.ConnectionState.Open)
{
this.m_conn.Close();
}
}
...
}

Now for my Dispose() and destructor, which is a Finalize() method, I have
the following...

~CDB()
{
this.Disconnect();
this.m_conn.Dispose();
}

public void Dispose()
{
this.Disconnect();
this.m_conn.Dispose();
System.GC.SuppressFinalize(this);
}
Now, when I create an instance of my wrapper, it can connect and perform
queries to the specified database. However, when the object goes out of
scope, it calls the destructor. In the destructor, it calls
Disconnect(),
where I get an error on the line that is "this.m_conn.Close()" stating
the
handle is not initialized, but I told the garbage collector to NOT call
Finalize() on the this.m_conn. I told it not to do this in the
constructor
of my wrapped object. So why is the m_conn being GC when I told it not
to?

Thank you all for your continued support and patience.
Trecius