How to correctly use the 'using' statement frees resources?

Ken H

Hi all,

Which of the following is correct? Is there a better way to make it more to save resources?

The first version:

public static DataTable ExecuteGetTable(string connstring) {

DataSet ds;
using (SqlConnection connection=new SqlConnection(connstring))
{

SqlCommand command = new SqlCommand(connstring);
SqlDataAdapter adapter = new SqlDataAdapter();
connection.Open();
adapter.SelectCommand = command;
ds = new DataSet();
adapter.Fill(ds);

}
return ds.Tables[0];

}

The second version:

public static DataTable ExecuteGetTable(string connstring) {

DataSet ds;
using (SqlConnection connection=new SqlConnection(connstring))
{

using (SqlCommand command = new SqlCommand(connstring))
{
using (SqlDataAdapter adapter = new SqlDataAdapter())
{
connection.Open();
adapter.SelectCommand = command;
ds = new DataSet();
adapter.Fill(ds);
}
}

}

return ds.Tables[0];

}

Thanks.

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
As a general rule, if an object implements IDisposable, then you should either call Dispose() manually when you've finished with it or wrap it in the using statement which does this automatically. This ensures that unmanaged resources are released in a timely manner.

So the second version is better practice than the first.

Having said this, whilst it's very important to call Dispose() on some objects such as connection or data reader objects, it's less important to call it on others such as command and data-adapter objects. Consequently many programmers (and even some MSDN examples) don't bother with the latter if the object will soon go out of scope as they know that when the destructor runs, just prior to garbage collection, it will clean up the unmanaged resources anyway.

Incidentally, even in these latter cases, calling Dispose() may improve performance because it may suppress finalization which means that the destructor won't be called at all.
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Mahesh Chand12y ago
As Vulpes said, you don't need to. If used properly, you will never need to call Dispose manually, unless you're creating your own custom classes.
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Vulpes12y ago
You don't need to - the using statement does it for you behind the scenes.
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Ken H12y ago
Well,How to call 'Dispose () ' in the second version?

Thanks.
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Guest User12y ago
The second version is better because we are advised to use the "using" statement when creating any object that implements the interface IDisposable.

And, It is highly recommended to Dispose IDisposable objects manually.

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