Error - Index refers beyond end of list

Problem saving file back to SharePoint with Excel COM lib. I open the file but it opens as 'xlviewer.xlsx' so I assume I need to overwrite the original file. (I removed the try/catch to do some error handling.) When I do I get this error: "Index refers beyond end of list" (error at line: 42 'SaveAs statement')

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Excel = Microsoft.Office.Interop.Excel;
using System.Reflection;
using System.IO;

namespace CopyInteractionIds
{
    class Program
    {
        static void Main(string[] args)
        {
            Excel.Application oApp;
            Excel._Workbook oWbFrom;
            Excel._Workbook oWbTo;
            Excel._Worksheet oWsFrom;
            Excel._Worksheet oWsTo;
            Excel.Range oRngFrom;
            Excel.Range oRngTo;

            //try
            //{
                oApp = new Excel.Application();
                oApp.Visible = true;
                Console.WriteLine("Opening source workbook");
                oWbFrom = (Excel._Workbook)(oApp.Workbooks.Open(@"path to my source wb"
                    , Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value
                    , Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value));
                Console.WriteLine("Opening edited workbook");
                oWbTo = (Excel._Workbook)(oApp.Workbooks.Open(@"https://path to my out wb"
                    , Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value
                    , Missing.Value, true, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value));
                Console.WriteLine("Copying data");
                oWsFrom = (Excel._Worksheet)oWbFrom.Worksheets.get_Item("Interaction Number Lookup");
                oWsTo = (Excel._Worksheet)oWbTo.Worksheets.get_Item("Interaction Number Lookup");
                oRngFrom = oWsFrom.get_Range("=OFFSET($A$1,0,0,COUNTA($A:$A),COUNTA($1:$1))",Missing.Value);
                oWsTo.get_Range("=OFFSET($A$1,0,0,COUNTA($A:$A),COUNTA($1:$1))", Missing.Value).Clear();
                oRngTo = oWsTo.get_Range("A1",Missing.Value);
                oRngFrom.Copy(oRngTo);
                Console.WriteLine("Saving edited file");
                oWbTo.SaveAs(@"path to out file"
         开发者_StackOverflow社区           , Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value
                    ,Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlShared, Missing.Value
                    , Missing.Value, Missing.Value, Missing.Value, Missing.Value);
                oWbTo.Close(false,Missing.Value,Missing.Value);
                oWbFrom.Close(false, Missing.Value, Missing.Value);
                oApp.Quit();
            //}
            //catch(Exception ex)
            //{
            //    Console.WriteLine("Unable to process job: {0}",ex.Message);
            //}

        }
    }
}

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I had a similar issue, it turned out my files were "damaged". Opening them all, having Excel repair them and then overwriting the damaged files seemed to do the trick for me.

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Someone else had the file open.