C# dotnet6 Azure Function App System.InvalidCastException when referencing a System.Drawing.Bitmap

Question

I have the following issue with a do.net 6 Azure Function App when using the v6 System.Drawing.Common package.

I'm getting the following error when referencing a bitmap, just wondering if anyone knows any work arounds for this.

2022-03-23T20:14:29.255 [Error] System.InvalidCastException: 
[A]System.Drawing.Bitmap cannot be cast to [B]System.Drawing.Bitmap. 
Type A originates from 'System.Drawing.Common, Version=4.0.2.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' 
in the context 'Default' 
at location 'D:\Program Files (x86)\SiteExtensions\Functions\4.1.3\32bit\System.Drawing.Common.dll'. 
Type B originates from 
'System.Drawing.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' in the context 'Default' at location
'D:\\home\\site\\wwwroot\\bin\\runtimes/win/lib/net6.0/System.Drawing.Common.dll

Obviously some issues with versioning going on here, but this is happening on an Azure Function App deployed with the .NET 6 runtime. I wonder why it's trying to cast it down to the v4.0.2 DLL when I never even reference that DLL anywhere in the project.

Anyone any ideas or potential work arounds for this?

Answer 1

I finally resolved this issue.

I had an embedded Bitmap image in a resource file, when I tried to use that image from the resource file, it was returned back as a Version=4.0.2.0 bitmap.

I'm in a .NET 6 Windows Function App, so it was referencing the v6 version of System.Drawing.Common, Version=6.0.0.0.

I changed the embedded image to be a byte steam, and could create a V6 Bitmap directly from that.

So it would appear that Azure Functions under the hood is using different libraries for embedded resources than the main environment would expect.