What are the uses of “using” in C#?

Question

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

Answer 1

Another example of a reasonable use in which the object is immediately disposed:

using (IDataReader myReader = DataFunctions.ExecuteReader(CommandType.Text, sql.ToString(), dp.Parameters, myConnectionString)) 
{
    while (myReader.Read()) 
    {
        MyObject theObject = new MyObject();
        theObject.PublicProperty = myReader.GetString(0);
        myCollection.Add(theObject);
    }
}