What are the uses of "using" in C#

User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. Can you elaborate on that? What are the uses of using ?

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The reason for the using statement is to ensure that the object is disposed as soon as it goes out of scope, and it doesn't require explicit code to ensure that this happens.

As in Understanding the 'using' statement in C#, the .NET CLR converts

using (MyResource myRes = new MyResource())
{
    myRes.DoSomething();
}

to

{ // Limits scope of myRes
    MyResource myRes= new MyResource();
    try
    {
        myRes.DoSomething();
    }
    finally
    {
        // Check for a null resource.
        if (myRes != null)
            // Call the object's Dispose method.
            ((IDisposable)myRes).Dispose();
    }
}

---

Since a lot of people still do:

using (System.IO.StreamReader r = new System.IO.StreamReader(""))
using (System.IO.StreamReader r2 = new System.IO.StreamReader("")) {
   //code
}

I guess a lot of people still don't know that you can do:

using (System.IO.StreamReader r = new System.IO.StreamReader(""), r2 = new System.IO.StreamReader("")) {
   //code
}

---

Things like this:

using (var conn = new SqlConnection("connection string"))
{
   conn.Open();

    // Execute SQL statement here on the connection you created
}

This SqlConnection will be closed without needing to explicitly call the .Close() function, and this will happen even if an exception is thrown, without the need for a try / catch / finally .

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