Question

I’m seeing a strange build bug a lot. Sometimes after typing some code we receive the following build error.

Class 'clsX' must implement 'Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs)' for interface System.ComponentModel.INotifyPropertyChanged'.   

And

'PropertyChanged' cannot implement 'PropertyChanged' because there is no matching event on interface 'System.ComponentModel.INotifyPropertyChanged'.

Those error should never go together! Usually we can just ignore the exception and build the solution but often enough this bug stops our build. (this happens a lot using Edit and Continue which is annoying)

We’re using Vb.net and c# mixed in one big solution.

Removing the PropertyChanged event and retyping the same code! sometimes fixes this.

Question:

Has anyone else seen this problem and has some suggestions how to prevent his?

We’re using a code generator that causes this error to surface but just editing some files manually triggers this exception too. This error occur’s on multiple machines using various setups.

Answer 1

Someone had the same exact issue discussed here. It sounds like there is an issue with this build picking up an old version of a binary. I would try the following in order:

• Verify all assembly references use project references where possible within the Visual Studio solution.
• Disable build parallelization in case there is some weird file locking issue with concurrent project builds. Go to Tools -> Options, Projects and Solutions -> Build and Run, then set “maximum number of parrellel project builds” to 1. Not the best solution but it may help narrow down the problem.
• Disable the Hosting Process in case it’s locking some file causing an assembly to not get rebuilt correctly. For C# project go to Project Properties, Debug tab, and uncheck “Enable the Visual Studio hosting process”. For VB.NET project you’ll need to Unload Project, Edit the project file, and add <UseVSHostingProcess>false</UseVSHostingProcess> to the PropertyGroup of each configuration. Again, not the best solution but you probably won’t notice a difference.
• Lastly, try doing a Clean + Build to try and resolve the issue when it occurs (I know this is not a fix but it’s easy enough to do), also Rebuild may be slightly different than Clean + Build so try the latter if the former doesn’t work.