BeginExecuteReader() Method
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'Declaration
Public Overloads Function BeginExecuteReader() As IAsyncResult |
Return Value
An
System.IAsyncResult interface that represents the asynchronous operation started by calling this method.
In the example below the easiest way of executing an asynchronous operation is shown. First, all components are set up and a connection is opened. Second, a data retrieval operation is started. The operation state (done or in progress) is checked and a report is written to the console. At last query results are sent to
Devart.Common.DbDataReader and rendered to the console.
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public void Async_Exec(DbConnectionBase myConnection)
{
DbCommandBase myCommand = (DbCommandBase)myConnection.CreateCommand();
myCommand.CommandText = "SELECT * FROM Test.Dept";
Console.WriteLine("Starting asynchronous retrieval of data...");
myConnection.Open();
IAsyncResult cres = myCommand.BeginExecuteReader();
if (cres.IsCompleted)
Console.WriteLine("Completed.");
else
Console.WriteLine("Have to wait for operation to complete...");
DbDataReader myReader = myCommand.EndExecuteReader(cres);
try
{
while (myReader.Read())
{
Console.WriteLine(myReader.GetInt32(0) + " " + myReader.GetString(1) + " " + myReader.GetString(2));
}
}
finally
{
myReader.Close();
myConnection.Close();
}
} |
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Public Sub Async_Exec(ByVal myConnection As DbConnectionBase)
Dim myCommand As DbCommandBase = myConnection.CreateCommand()
myCommand.CommandText = "SELECT * FROM Test.Dept"
Console.WriteLine("Starting asynchronous retrieval of data...")
myConnection.Open()
Dim cres As IAsyncResult = myCommand.BeginExecuteReader()
If cres.IsCompleted Then
Console.WriteLine("Completed.")
Else
Console.WriteLine("Have to wait for operation to complete...")
End If
Dim myReader As DbDataReader = myCommand.EndExecuteReader(cres)
Try
While myReader.Read()
Console.WriteLine(String.Concat(myReader.GetInt32(0), " ", myReader.GetString(1), " ", myReader.GetString(2)))
End While
Finally
myReader.Close()
myConnection.Close()
End Try
End Sub |
