title: How to Save/Overwrite existing Excel file with Excel Interop - C#
body: <p>Is there a way to save changes to an excel spreadsheet through the excel interop (in this case I am adding a worksheet to it) without having it prompt the user if they want to overwrite the existing file with the changes.  I do not want the user to even see the spreadsheet open in my application so having a message box popping up asking them if they want to overwrite the file seems very out of place and possibly confusing to the user.  </p>
  
  <p>I am using the workbook.SaveAs(fileloaction) method.  </p>
  
  <p>Here is where I am initializing the COM reference objects for the excel interop.</p>
  
  <pre><code>private Excel.Application app = null;
      private Excel.Workbook workbook = null;
  
      public Excel.Workbook Workbook
      {
          get { return workbook; }
          set { workbook = value; }
      }
      private Excel.Worksheet worksheet = null;
      private Excel.Range workSheet_range = null;
  </code></pre>
  
  <p>Below is the code I am using to close/save the excel file.  The workbook.close() method line is the one that is reportedly throwing the unhandled exception. </p>
  
  <pre><code> workbook.Close(true, startForm.excelFileLocation, Missing.Value);
              Marshal.ReleaseComObject(app);
              app = null;
              System.GC.Collect();
  </code></pre>