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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// Description: Default async scheduler for data operations.
//
using System.Collections;
using System.Threading;
using System.Windows;
namespace MS.Internal.Data
{
internal class DefaultAsyncDataDispatcher : IAsyncDataDispatcher
{
//------------------------------------------------------
//
// Interface: IAsyncDataDispatcher
//
//------------------------------------------------------
/// <summary> Add a request to the dispatcher's queue </summary>
void IAsyncDataDispatcher.AddRequest(AsyncDataRequest request)
{
lock (_list.SyncRoot)
{
_list.Add(request);
}
ThreadPool.QueueUserWorkItem(new WaitCallback(ProcessRequest), request);
}
/// <summary> Cancel all requests in the dispatcher's queue </summary>
void IAsyncDataDispatcher.CancelAllRequests()
{
lock (_list.SyncRoot)
{
for (int i = 0; i < _list.Count; ++i)
{
AsyncDataRequest request = (AsyncDataRequest)_list[i];
request.Cancel();
}
_list.Clear();
}
}
//------------------------------------------------------
//
// Private methods
//
//------------------------------------------------------
// Run a single request. This method gets scheduled on a worker thread
// from the process ThreadPool.
void ProcessRequest(object o)
{
AsyncDataRequest request = (AsyncDataRequest)o;
// PreSharp uses message numbers that the C# compiler doesn't know about.
// Disable the C# complaints, per the PreSharp documentation.
#pragma warning disable 1634, 1691
// PreSharp complains about catching NullReference (and other) exceptions.
// In this case, these are precisely the ones we want to catch the most,
// so that a failure on a worker thread doesn't affect the main thread.
#pragma warning disable 56500
// run the request - this may take a while
try
{
request.Complete(request.DoWork());
}
// Catch all exceptions. There is no app code on the stack,
// so the exception isn't actionable by the app.
// Yet we don't want to crash the app.
catch (Exception ex)
{
if (CriticalExceptions.IsCriticalApplicationException(ex))
throw;
request.Fail(ex);
}
catch // non CLS compliant exception
{
request.Fail(new InvalidOperationException(SR.Format(SR.NonCLSException, "processing an async data request")));
}
#pragma warning restore 56500
#pragma warning restore 1634, 1691
// remove the request from the list
lock (_list.SyncRoot)
{
_list.Remove(request);
}
}
//------------------------------------------------------
//
// Private data
//
//------------------------------------------------------
ArrayList _list = new ArrayList();
}
}
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