when does dispose method is called in using block

Question

I am trying to test this piece of code by putting in breakpoints. I want to make sure that after the using block the dispose method is called and the resources (SqlCommand), is gracefully released. However nowhere in the using block I hit any dispose?

    using (SqlCommand command = new SqlCommand(queryString, connection))
{
    command.CommandType = CommandType.Text;
    command.Parameters.Add("@OrganizationID", SqlDbType.Int);
    command.Parameters["@OrganizationID"].Value = organizationId;
    connection.Open();
    SqlDataReader sqlDataReader = command.ExecuteReader(CommandBehavior.CloseConnection);

    try
    {
        while (sqlDataReader.Read())
        {
            //do something 
        }
    }
    finally
    {
        sqlDataReader.Close();
    }
}

Answer 1

The call to Dispose of IDisposable happens after the using block has finished execution, normally or abnormally (i.e. through an exception).

The only way you could catch the call in a source-level debugger is when you have the source code for your IDisposable - in your case it would be the source code of SqlCommand class.

One simple way of checking the way this works is to make your own IDisposable implementation, put it into a using block, and observe its behavior. The call to Dispose should follow immediately after completion of the using block.