Establish Connection to existing Excel Application and Run an Excel macro C#

Question

All,

Apologies if this is a very basic question and has been asked before, I predominately write in VBA / JAVA. However a project I am working on requires a C# script. Which carries out 3 simple steps:

1. Target a excel workbook which is already open. File path:

   \\Csdatg04\\psproject\\Robot\\Peoplesoft To LV\\Master Files - Do not use\\Transactions into LV Template.xlsm

2. Populate cells A1,A2 & A3 with three variables already retrieved earlier in the automation.

3. Run a macro stored within the filepath mentioned above Macro name "ControlMacroACT"

The code I have developed is below, however in each stage identified above I am encountering errors (Probably basic errors).

Error 1: This line of code is to open a workbook I would like this to target an already active workbook.

Error 2: Worksheet not found

public void RunActualsMacro(string Filepath, string Period, String FiscalYear)
    {
        //~~> Define your Excel Objects
        Excel.Application xlApp = new Excel.Application();

        Excel.Workbook xlWorkBook;

        //~~> Start Excel and open the workbook.
        //Error 1
        xlWorkBook = xlApp.Workbooks.Open("\\Csdatg04\\psproject\\Robot\\Peoplesoft To LV\\Master Files - Do not use\\Transactions into LV Template.xlsm");

        // Populat Cells A1,A2,A3 with string variables
        // Error 2 Worksheet not found
        worksheet.Rows.Cells[1, 1] = Filepath;
        worksheet.Rows.Cells[2, 1] = Period;
        worksheet.Rows.Cells[3, 1] = FiscalYear;


        //~~> Run the macro ControlMacroAct
        xlApp.Run("ControlMacroACT");

        //~~> Clean-up: Close the workbook
        xlWorkBook.Close(false);

        //~~> Quit the Excel Application
        xlApp.Quit();

    }

Any help would be much appreciated.

Answer 1

You need to use Marshal.GetActiveObject, and this code is roughly right, but cannot test right now.

public void RunActualsMacro(string Filepath, string Period, String FiscalYear)
{
    //~~> Define your Excel Objects
    Excel.Application xlApp = null;

    Excel.Workbook xlWorkBook;

    //~~> Start Excel and open the workbook.
    //handle errors below
    try {
        xlApp = (Excel.Application) System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
    } catch {
        //perhaps exit - or throw??
    }

    xlWorkBook = xlApp.Workbooks["Transactions into LV Template.xlsm"];

    // Populat Cells A1,A2,A3 with string variables
    Excel.Worksheet ws = xlWorkBook.Worksheets["Sheet1"] //what the tab name of sheet
    ws.Cells[1, 1] = Filepath;
    ws.Cells[2, 1] = Period;
    ws.Cells[3, 1] = FiscalYear;


    //~~> Run the macro ControlMacroAct
    xlApp.Run("ControlMacroACT");

    //~~> Clean-up: Close the workbook
    xlWorkBook.Close(false);

    //~~> Quit the Excel Application
    xlApp.Quit();

}