CHAPTER 1 ■ ASP.NET 4.5 DATA SOURCES
11
catch (Exception)
{
//Log Exception
}
}
You will notice that the main thread is not blocked, and you can continue to see the results inside the while loop
that checks for the IAsyncResult IsCompleted property. A simple callback handler will look like the following:
private static void CallBack(IAsyncResult result)
{
try
{
var command = (SqlCommand)result.AsyncState;
command.EndExecuteNonQuery(result);
}
catch (Exception)
{
//Log Exception
}
}
For a simple asynchronous execution of the command, this is lot of code. You will find out how this is simplified
in .NET Framework 4.5.
Note ■ In order for the asynchronous operation to work, the attribute “Asynchronous Processing=true” needs to be
set on the connection string element of your configuration file.
Async Programming Model in .NET Framework 4.5
The asynchronous programming model just discussed has not been deprecated in .NET Framework 4.5. It
continues to be supported; however, the preferred approach is to use the new model leveraging a task-based parallel
programming pattern along with async and await modifiers. It is very important that you implement the modifiers
appropriately. The implementation can become synchronous unless one follows an async call by one or more await
modifiers. The async modifier indicates an asynchronous operation, and when the program execution encounters the
await modifier, it exits the current method. When the forked task finishes, execution resumes in the method.
Caution ■ Asynchronous operations are not supported if the attribute "Context Connection" is set to "true" in the
connection string.
The ADO.NET Async programming model in .NET Framework 4.5 exposes an equivalent asynchronous method
for every synchronous method exposed by the data providers. Continuing with the previous example, the SqlCommand
ExecuteNonQuery command has an equivalent asynchronous method named ExecuteNonQueryAsync. It accepts a
CancellationToken as a parameter allowing the operation to be aborted before the command timeout elapses.
Now let’s take a look at how the programming model significantly reduces the lines of code you have to write for
the same operation.
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