Hi.

In the sample source code, there are many lines of code similiar to this

using (DataSet temp = SomeMethodWhichReturnsDataSet()) {
 return temp;
}

As far as I know, the purpose of this using block is to force Dispose method to be called on temp object when the control leaves the using block. In this way, we can releases any unmanaged resources used by temp object.

My Question is why do we need to use using block at all????

Using always calls Dispose, even if an exception is raised. This is just easier than using "try..finally" all over the place.

The only time you really need to call Dispose (whether it's directly called or indirectly called) is when there's unmanged resources involved.

The key unmanaged resource is normally ADO.NET connections. However, in ASP.NET you typically have a pool of connections managed for you automatically, so there's less need to call Dispose for ASP.NET.

Many people consider it "good practice" to call Dispose anytime a class implements it. It's mostly C++ programmers who migrate to C# that have this outlook, but it's probably the "most correct" outlook, anyway.

Eric