Inserting Sheet from another Workbook in Excel Add-in

Question

I am trying to copy a sheet from an existing Excel Workbook and paste it into the current workbook using an Excel Add-in. I am using the following code but it is throwing an exception:

private void insertSamplingWksht_Click(object sender, RibbonControlEventArgs e)
{
     Microsoft.Office.Interop.Excel.Application xlApp = new    
     Microsoft.Office.Interop.Excel.Application();
     Workbook templateWorkbook = xlApp.Workbooks.Open(templatePath);
     Worksheet from = (templateWorkbook.Sheets[1] as Worksheet); // Get first sheet
     Worksheet to = (Globals.ThisAddIn.Application.ActiveWorkbook.ActiveSheet as Worksheet);
     from.Copy(to, Type.Missing); // Throws System.Runtime.InteropServices.COMException: 'No such interface supported'
 }

I also tried the following which did not work either.

private void insertSamplingWksht_Click(object sender, RibbonControlEventArgs e)
{
    string templatePath = @"path to file";

    Microsoft.Office.Interop.Excel.Application xlApp = Globals.ThisAddIn.Application;
    var activeWkbName = xlApp.ActiveWorkbook.Name;

    int beforeCount = xlApp.Workbooks.Count; // 1

    var templateWorkbook = xlApp.Workbooks.Open(templatePath);
    var from = (templateWorkbook.Sheets[1] as Microsoft.Office.Interop.Excel.Worksheet);

    int afterCount = xlApp.Workbooks.Count; // also 1

    xlApp.Workbooks[activeWkbName].Activate(); // COMException: 'Invalid index. 
    from.Copy(xlApp.ActiveWorkbook.ActiveSheet, Type.Missing);
}

Answer 1

It was a strange Excel issue. We had disabled the Excel welcome page via a registry key at HKEY_CURRENT_USER\\Software\\Microsoft\\Office\\16.0\\Common\\General\\DisableBootToOfficeStart. For some strange reason this stopped this code from working as expected.

Answer 2

Try this

            // no need to open another Excel instance
            Microsoft.Office.Interop.Excel.Application xlApp = Globals.ThisAddIn.Application;
            // get the name of the active workbook to be able to return back
            var activeWkbName = xlApp.ActiveWorkbook.Name;

            // open the template workbook - which will become active then
            var templateWorkbook = xlApp.Workbooks.Open(templatePath);
            var from = (templateWorkbook.Sheets[1] as Microsoft.Office.Interop.Excel.Worksheet); 

            // active the original one
            xlApp.Workbooks[activeWkbName].Activate();
            from.Copy(xlApp.ActiveWorkbook.ActiveSheet, Type.Missing);