Open excel workbook but set calculations to manual

Question

I have tried a few options but none seem to work, and some send errors.

Please let me know what I am doing wrong

public string Main(String wbPath, String wbName)
{
    string cName = "";
    Excel.Application xlApp;
    Excel.Workbook xlWB;
    Excel.Worksheet xlWS;


    xlApp = new Excel.Application();
    xlApp.DisplayAlerts = false;
    xlApp.Calculation = Excel.XlCalculation.xlCalculationManual;       //Error occurs here 

    xlWB = xlApp.Workbooks.Open(wbPath + wbName);

    xlWB.SaveAs("vFile.html", Microsoft.Office.Interop.Excel.XlFileFormat.xlHtml);
    cName = xlWB.FullName;
    xlWB.Close();


    xlApp.Quit();

    return cName;
}

Error code:

{"Exception from HRESULT: 0x800A03EC"}

Answer 1

You must open the workbook before setting the xlApp.Calculation:

static void Main(string[] args)
{
    string cName = "";

    var xlApp = new Application();

    var xlWB = xlApp.Workbooks.Open("youpathgoeshere", Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
    xlApp.Calculation = XlCalculation.xlCalculationManual;

    var xlWS = new Worksheet();

    xlWB.SaveAs("vFile.html", Microsoft.Office.Interop.Excel.XlFileFormat.xlHtml);
    cName = xlWB.FullName;
    xlWB.Close();

    xlApp.Quit();

}