Opening an excel file from button click on a windows form

Question

private void btnOpenReport_Click(object sender, EventArgs e)
{  
    if (System.IO.File.Exists(outputFilePath))
    {
        Process.Start(new ProcessStartInfo("excel.exe", " /select, " + outputFilePath.Replace("\\\\", "\\")));
     }
}

Solution

Probably you should just start the Excel file directly with property UseShellExecute to true, which is the default, and it will launch the default associated program, most likely Excel itself:

Process.Start(outputFilePath);

Another matter is why you are doing that Replace, but that's probably off-topic here.