I remove OWIN from project and implemented custom forms authentication. However problem with LS still occurs. I thought that problem is with async API of OWIN and WebAPI, but problem is maybe in LS. I ensured one thread in request with SAC code.
Then I try this simple code in Global.asax
protected void Application_PreRequestHandlerExecute(object sender, EventArgs e)
{
using(ServerApplicationContext ctx = ServerApplicationContext.CreateContext())
{
var x = ctx.Dataworkspace.ApplicationData.InvoiceOuts.GetQuery().Execute();
}
}
Stop iisexpress server (important), build and debug.
And run multiple client requests in one time on this application (using console app).
For some first requests NullReferenceException in Microsoft.LightSwitch occured.
I think it's thread specific error in LS code.
Workaround for this errors is following SACDispatcher class (If NullReferenceException occurs in LS, repeat SAC code)
public class ServerApplicationContextDispatcher
{
[ThreadStatic]
private static ServerApplicationContextDispatcher instance = null;
public static ServerApplicationContextDispatcher Instance
{
get
{
if(instance == null)
{
instance = new ServerApplicationContextDispatcher();
}
return instance;
}
}
private const int repeatThreshold = 2;
private int invokeCounter;
public void Invoke(Action<ServerApplicationContext> action)
{
InitializeCounter();
InvokeInner(action);
}
private void InitializeCounter()
{
invokeCounter = 1;
}
private void InvokeInner(Action<ServerApplicationContext> action)
{
try
{
using(ServerApplicationContext ctx = ServerApplicationContext.CreateContext())
{
action(ctx);
}
}
catch (Exception ex)
{
if (CanRepeatInvoke(ex))
{
IncrementCounter();
Exception exception = RepeatInvokeWithExceptionHandling(action);
if(exception != null)
{
throw new Exception(exception.Message, ex);
}
}
else
{
throw;
}
}
}
private bool CanRepeatInvoke(Exception ex)
{
return IsNullReferenceExceptionInLightswitch(ex) && invokeCounter <= repeatThreshold;
}
private bool IsNullReferenceExceptionInLightswitch(Exception ex)
{
Exception current = ex;
while (current.InnerException != null)
{
current = current.InnerException;
}
return current is NullReferenceException && current.Source == "Microsoft.LightSwitch";
}
private void IncrementCounter()
{
invokeCounter++;
}
private Exception RepeatInvokeWithExceptionHandling(Action<ServerApplicationContext> action)
{
Exception exception = null;
try
{
InvokeInner(action);
}
catch (Exception ex)
{
exception = ex;
}
return exception;
}
}
Usage:
ServerApplicationContextDispatcher.Instance.Invoke((ctx) =>
{
var x = ctx.DataWorkspace.ApplicationData.InvoiceOuts.GetQuery().Execute();
});
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