Unable to cast COM object of type 'Microsoft.Office.Interop.Excel.WorksheetClass'

Question

I'm trying to create and save a new excel document in C# from a bunch of aggregate data. Right now, I'm just trying to get the basics working as far as editing the table cells, etc. Here's me just trying to set the contents of one cell:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Microsoft.Office.Interop.Excel;

namespace DebugReport
{
    class MonumentDebugReport
    {
        static void Main(string[] args)
        {    
            Worksheet spreadsheet = new Worksheet();

            spreadsheet.Cells[0, 0] = "stuff";
       }
    }
}

This returns:

Unable to cast COM object of type 'Microsoft.Office.Interop.Excel.WorksheetClass' to interface type 'Microsoft.Office.Interop.Excel._Worksheet'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D8-0000-0000-C000-000000000046}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

on the line in which I'm setting the cell. To me, this looks exactly like most of the examples / tutorials I've seen, and I can't find anything in the C# documentation to indicate that this wouldn't work.

Answer 1

Like Hans already said you need to create an Excel application first, then you add a Workbook to it, then you add a Worksheet ( or try to access an already existing Sheets[1] )

Give using Microsoft.Office.Interop.Excel and alias

using Excel = Microsoft.Office.Interop.Excel

and then

Excel.Application xlApp = new Excel.Application();
xlApp.Visible = true;
Excel.Workbook xlWb = xlApp.Workbooks.Add() as Excel.Workbook;
Excel.Worksheet xlSheet = xlWb.Sheets[1] as Excel.Worksheet;
Excel.Range range = xlSheet.get_Range("A1");

range.Value = "hello world!";

and then have a look at How to properly clean up Excel interop objects