Issue about embedded interop types

[KinsonWong]

Coding with Net Framework 4.8

I want to Refer "Microsoft.Office.Interop.Excel" which is embedded interop types while compile a class.

If I use dynamic type,it can compile succefully and run.

public class Module{
		public void Main(){
			dynamic xlApp = System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
			dynamic wb = xlApp.Workbooks.Add();
			MessageBox.Show(wb.Name);
		}
	}

When I change the Type, compile Error occur.

public class Module{
		public void Main(){
			var xlApp = (Microsoft.Office.Interop.Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
			var wb = xlApp.Workbooks.Add();
			MessageBox.Show(wb.Name);
		}
	}

[RickStrahl]

You need to add a reference to the Interop assembly most likely.