BeginExecuteNonQuery(AsyncCallback,Object) Method

In This Topic

Starts an asynchronous invocation of an ExecuteNonQuery method with information for callback function.

Syntax

Visual Basic
C#

'Declaration
 
Public Overloads Function BeginExecuteNonQuery( _
   ByVal callback As AsyncCallback, _
   ByVal stateObject As Object _
) As IAsyncResult

public IAsyncResult BeginExecuteNonQuery( 
   AsyncCallback callback,
   object stateObject
)

Parameters

callback: The delegate to call when the asynchronous invoke is complete. If callback is a null reference (Nothing in Visual Basic), the delegate is not called.
stateObject: State information that is passed on to the delegate.

Return Value

An System.IAsyncResult interface that represents the asynchronous operation started by calling this method.

Remarks

BeginExecuteNonQuery method enables you to execute a query on a server without having current thread blocked. In other words, your program can continue execution while the query runs on a database so you do not have to wait for it.

To start running a query, you have to call BeginExecuteNonQuery method, which in turn invokes appropriate actions in another thread. Return value of this method must be assigned to System.IAsyncResult object. After executing this method program flow continues.

When you are ready to accept query results, call EndExecuteNonQuery. If at the moment you call this function the query execution has not yet been finished, application stops and waits till the function returns number of rows affected by the query.

Refer to "Asynchronous Query Execution" article for detailed information.

Example

In the example below an easiest way of executing an asynchronous operation is shown. First, all components are set up and a connection is opened. Second, a query execution is started. The operation state (done or in progress) is checked and a report is written to the console. At last query result is rendered.

csharp

static void Async_Exec(DbConnectionBase myConnection)
{
  DbCommandBase myCommand = (DbCommandBase)myConnection.CreateCommand();
  myCommand.CommandText = "UPDATE Test.Dept SET DName='New Department' WHERE DeptNo=10";
  Console.WriteLine("Starting asynchronous query execution...");
  myConnection.Open();
  IAsyncResult cres = myCommand.BeginExecuteNonQuery(null, null);
  if (cres.IsCompleted)
    Console.WriteLine("Completed.");
  else
    Console.WriteLine("Have to wait for operation to complete...");
  try
  {
    int RowsAffected = myCommand.EndExecuteNonQuery(cres);
    Console.WriteLine("Done. Rows affected: " + RowsAffected.ToString());
  }
  catch (Exception e)
  {
    Console.WriteLine("An exception has occurred: " + e.Message);
  }
  finally
  {
    myConnection.Close();
  }
}

Visual Basic

Public Sub Async_Exec(ByVal myConnection As DbConnectionBase)
  Dim myCommand As DbCommandBase = myConnection.CreateCommand()
  myCommand.CommandText = "UPDATE Test.Dept SET DName='New Department' WHERE DeptNo=20"
  Console.WriteLine("Starting asynchronous query execution...")
  myConnection.Open()
  Dim cres As IAsyncResult = myCommand.BeginExecuteNonQuery(Nothing, Nothing)
  If cres.IsCompleted Then
    Console.WriteLine("Completed.")
  Else
    Console.WriteLine("Have to wait for operation to complete...")
  End If
  Try
    Dim RowsAffected As Integer = myCommand.EndExecuteNonQuery(cres)
    Console.WriteLine(String.Concat("Rows affected: ", RowsAffected.ToString()))
  Catch e As Exception
    Console.WriteLine(String.Concat("An exception has occurred: ", e.Message))
  Finally
    myConnection.Close()
  End Try
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

DbCommandBase Class
DbCommandBase Members
Overload List

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