The BeginExecuteNonQuery method starts the process of asynchronously executing a Transact-SQL statement or stored procedure that does not return rows, so that other tasks can run concurrently while the statement is executing. When the statement has completed, developers must call the EndExecuteNonQuery method to finish the operation. The BeginExecuteNonQuery method returns immediately, but until the code executes the corresponding EndExecuteNonQuery method call, it must not execute any other calls that start a synchronous or asynchronous execution against the same SqlCommand object. Calling the EndExecuteNonQuery before the command's execution is completed causes the SqlCommand object to block until the execution is finished.
Note that the command text and parameters are sent to the server synchronously. If a large command or many parameters are sent, this method may block during writes. After the command is sent, the method returns immediately without waiting for an answer from the server--that is, reads are asynchronous.
Because this overload does not support a callback procedure, developers must either poll to determine whether the command has completed, using the IsCompleted property of the IAsyncResult returned by the BeginExecuteNonQuery method; or wait for the completion of one or more commands using the AsyncWaitHandle property of the returned IAsyncResult.