This error can happen when a wrong statement / codeline will be inserted in the text field
As it is C#, we also suffer sometimes, that also correct statements will not pass the compiler check
ensure that the statement is correct
delete the Value to save
save XAML
insert the statement again (best paste from clipboard the correct one
type in a very simple statement like “Hello World” for a string variable assignment also try
Try also to delete the Assign activity and remodel it again
As mentioned:
In majority of cases, when we saw the error, it was more about the XML interpretation of the code entered within the field. And it was not about missing dependecies. So we were also not forced to add any packages (e.g. …XML…) to the project