While working on my project, I got this error:
The item \"...\" was specified more than once in the \"Resources\" parameter. Duplicate items are not
This happen when you change name form it duplicate resources file of form.
You open old copy all items and paste to new resource then delete old res file.
Rebuild Solutions.
To fix the issue I browsed to [obj > Debug] and [obj > release] and deleted any files which referenced the word resources. After this, my project built successfully.
I guess the item "..." is a form, then:
I received this error after I copy and paste Form1 (for example) in my project.I rename Copy in Form2, but Form2 had next line in *.cs "public partial class Form1". As i understand after copying class name didn't change. I resolved this problem by adding a new form and copying there controls from my old form. The Old form was deleted.
A slightly simpler way ..
No need to restart Solution or move the form.
Create a backup of both the .cs and .designer.cs file which is giving the error and then delete that file from the project. Rebuild the solution and then copy back both .cs and .designer.cs files. Finally, rebuild the solution again.