Property, indexer, or event 'Range' is not supported by the language; try directly calling accessor method 'Microsoft.Office.Interop.Excel._Worksheet.

A worksheet Range cannot be called directly as shown below

Excel.Worksheet wks = Globals.ThisAddIn.Application.ActiveSheet as Excel.Worksheet;

wks.Range("A1").value2 = "Hi";

Instead use the get_Range Method of Worksheet Class

Excel.Worksheet wks = Globals.ThisAddIn.Application.ActiveSheet as Excel.Worksheet;

0020Excel.Range myRange = wks.get_Range("A1", System.Type.Missing);

myRange.Value2 = "Hello";

See also :

Object Arrays in C# using Indexers

Properties in .NET / Get and Set Methods in .NET