NullReferenceException from AlphaImage.CreateFromResource()

Question

I am using the AlphaMobileControls library for the .NET Compact Framework. I am using AlphaImage.CreateFromResource(imageResourceName) to create an AlphaImage object. The problem is that this method is throwing a NullReferenceException. Looking at the code for this method, the problem is that this line of code is returning null:

MemoryStream stream = 
                (MemoryStream)Assembly.GetCallingAssembly().GetManifestResourceStream(imageResourceName);

This was working fine before, and now it is not and I can't figure out why. It seems that I am passing a valid resource name. It is a resource that I added using the Resources tab of the project properties. Also in the Resources folder the image file is there and the Build Action is set to Embedded Resource. I even used this code to retrieve the available resources, and the one I am using was one of the returned values:

string[] names = Assembly.GetCallingAssembly().GetManifestResourceNames();

Then I was thinking that maybe by the time the AlphaImage.CreateFromResource() method code is running the available resources might be different. So I modified the code to include the above statement and then throw an InvalidOperationException if the passed resource is not an available resource. When I run the program and step through the code with the debugger, the added code is not there anymore and an InvalidOperationException is not thrown and the code will run until the NullReferenceException occurs. I searched my projects to see if maybe there was a reference to another version of AlphaMobileControls other than the one with the modified code, but I could not find any.

Any help will be appreciated, thanks in advance!

Answer 1

Inspect the result from Assembly.GetCallingAssembly().GetManifestResourceNames(); and see whether the resource name you are looking for appears here. When it doesn't, your settings on the properties of the resource (specifically "Build action: Embedded resource") will probably be set incorrect. Otherwise, maybe a folder has been renamed and you need to change the value of imageResourceName.

Answer 2

Aren basically answered this for me with his comment. You need to call AlphaImage.CreateFromResource() from the assembly that has the required resource. Thanks Aren.

The change I made that caused this to stop working was that I moved the class that was calling AlphaImage.CreateFromResource() into a separate library from the one that had the image resource. Therefore Assembly.GetCallingAssembly() is returning the assembly that does not have the resource.