MySolutions MainWindowsProject References: MyFirstSolutionProject - MainForm.cs - has a "using MyFirstSolutionProject;" - has a menu click method that has this code: // updated implementation: { MyFirstSolutionClass fs = new MyFirstSolutionClass(); fs.OpenEditor(); } MyFirstSolutionProject References: SolutionBaseFormsProject - FirstSolutionEditor : BaseEditor // New class added - MyFirstSolutionClass public void OpenEditor() { FirstSolutionEditor fse = new FirstSolutionEditor(); fse.Show(); } SolutionBaseFormsProject - BaseEditor.cs