Load Operation Failed

dr63 — 10/3/2011 6:46:57 PM

I've a domain service which communicates the database server and fetches the results from silver light hosted web app. It works find when I am debugging from "VS Development Server". But it throws the following error when I do it from IIS 7.

Message: Unhandled Error in Silverlight Application Object reference not set to an instance of an object.
at MyViewModel.invOp_Completed(Object sender, EventArgs e)
at System.ServiceModel.DomainServices.Client.OperationBase.Completeed(Exception error)
at System.ServiceModel.DomainServices.Client.InvokeOperation.Complete(Exception error)
at System.ServiceModel.DomainServices.Client.DomainContext.CompleteInvoke(IAsyncResult asyncResult)
at System.ServiceModel.DomainServices.Client.DomainContext.<>c__DisplayClass38.b__34(Object )

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brian.noyes — 10/5/2011 2:22:44 AM

That is not much to go by since it is a basic null reference exception. If I had to guess based on experience, because IIS is running under a least privileged account by default, and the VS Development Server is running as you, the logged in user (which for most developers means admin), it is probably a permissions thing that means something in your code is not getting initialized and there is a subsequent null reference exception being thrown.

Some debugging tips to try:

- Add an override for the Initialize method and set a breakpoint in there. If you are not getting there, your domain service is not even getting loaded.

- Put a breakpoint in your query method and see if it is being called

- Run Fiddler or a similar HTTP debugging tool and inspect the error message being returned at a wire level

- double check the structure of your MyViewmodel.invOp_Completed method and make sure there are no accidental attempts to use something that is not initialized in there (possibly because there is really an error happening server side).

If those dont work, make sure you have read my article on debugging RIA apps:

http://www.silverlightshow.net/items/WCF-RIA-Services-Part-8-Testing-and-Debugging.aspx

And if that still fails, try posting a little more information here and I will see if I can help.

Brian

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Load Operation Failed

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