BeginOpen Method

In This Topic

Starts an asynchronous invocation of an Open method.

Syntax

Visual Basic
C#


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


public IAsyncResult BeginOpen( 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

BeginOpen method enables you to open a connection to server without having current thread blocked. In other words, your program can continue execution while the connection is establishing so you do not have to wait for it.

To start opening a connection, you have to call BeginOpen 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 use the connection, call EndOpen. If at the moment you call this method the negotiation process has not yet been finished, application stops and waits till the function returns which means that the connection is open.

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

Example

This sample shows how to implement asynchronous opening of a connection.

csharp


public void AsyncOpen(DbConnectionBase myConnection) { IAsyncResult myAsyncResult = myConnection.BeginOpen(null, null); DbCommandBase myCommand = (DbCommandBase)myConnection.CreateCommand(); myCommand.CommandText = "INSERT INTO Test.Dept(DeptNo, DName) Values('100', 'DEVELOPMENT')"; //some operations here myConnection.EndOpen(myAsyncResult); try { myCommand.ExecuteNonQuery(); } finally { myConnection.Close(); } }

public void AsyncOpen(DbConnectionBase myConnection)
{
  IAsyncResult myAsyncResult = myConnection.BeginOpen(null, null);
  DbCommandBase myCommand = (DbCommandBase)myConnection.CreateCommand();
  myCommand.CommandText = "INSERT INTO Test.Dept(DeptNo, DName) Values('100', 'DEVELOPMENT')";
  //some operations here
  myConnection.EndOpen(myAsyncResult);
  try
  {
    myCommand.ExecuteNonQuery();
  }
  finally
  {
    myConnection.Close();
  }
}

Visual Basic


Public Sub AsyncOpen(ByVal myConnection As DbConnectionBase) Dim myAsyncResult As IAsyncResult = myConnection.BeginOpen(Nothing, Nothing) Dim myCommand As DbCommandBase = myConnection.CreateCommand() myCommand.CommandText = "INSERT INTO Test.Dept(DeptNo, DName) Values('110', 'QA')" ' some operations here myConnection.EndOpen(myAsyncResult) Try myCommand.ExecuteNonQuery() Finally myConnection.Close() End Try End Sub

Public Sub AsyncOpen(ByVal myConnection As DbConnectionBase)
  Dim myAsyncResult As IAsyncResult = myConnection.BeginOpen(Nothing, Nothing)
  Dim myCommand As DbCommandBase = myConnection.CreateCommand()
  myCommand.CommandText = "INSERT INTO Test.Dept(DeptNo, DName) Values('110', 'QA')"
  ' some operations here
  myConnection.EndOpen(myAsyncResult)
  Try
    myCommand.ExecuteNonQuery()
  Finally
    myConnection.Close()
  End Try
End Sub

Reference

DbConnectionBase Class
DbConnectionBase Members

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