Xamarin Form Error Value cannot be null. Parameter name: type

Question

All day I was receiving this very clear (not the sarcasm) error message "Value cannot be null. Parameter name: type" I was hitting my head against the wall slowly decomposing my code until I could figure out the exact cause of the problem. After much tedious deconstruction I discovered that I had an error in my GestureRecognizers section. The problem was that I accidentally typed Command to try to pass a parameter instead of CommandParameter.

My original code generating the error looked like this.

<Label.GestureRecognizers>
    <TapGestureRecognizer Tapped="Value_Tapped" Command="language" />
</Label.GestureRecognizers>

The corrected code is this:

<Label.GestureRecognizers>
    <TapGestureRecognizer Tapped="Value_Tapped" CommandParameter="language" />
</Label.GestureRecognizers>

I hope this helps someone else in the future.

Answer 1

I managed to fix the issue after following every steps from this post:

• Clean the solution.
• Close Visual Studio.
• Delete the bin and obj directories from each project in the solution (YourProject, YourProject.Android, YourProject.iOS)
• Restart Visual Studio.
• Build each project individually - NOT rebuild the solution.
• Rebuild Solution.

Answer 2

It appears if you try to set the Command property to something Xamarin Forms does not know you will get this error. If you get the error I suggest double checking all the non-intelisense correct parameters in your code.