The Behavior of a Using Statement

14 November, 2008 § Leave a comment

C# comes right out of the box with it’s own garbage collector. When objects are no longer referenced and go out of scope, they are then marked for garbage collection. Some of these objects may have special properties.

They may carry handles to files, connections to databases, etc. When the garbage collector picks these objects up, it doesn’t really know what to do with these associations.

Cleverly, there is an interface to solve this. It’s called IDisposable. With IDisposable, you are required to implement one function, Dispose(). Dispose can be compared to the C++ destructor. File buffers and database connections can all be closed right within Dispose.

This seems nice, but awkward to call Dispose on an object when you are done with it. It would be nice to just nest that object in a block statement so it is easier to see from a glance when a specific object is not needed. It would also be nice if that Dispose method could be called when the block is finished.

This brings us towards a using statement. Here is an example:

ResultSet resultSet;
using( var sqlConnection = new SqlConnection() )
{
  resultSet = sqlConnection.ExecuteQuery( "select * from `products`" );
  sqlConnection.ExecuteNonQuery( "delete from `products`" );
}
...
...  //messing around with the result set
...
return resultSet;

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