Question

I’ve searched around for the answer to this many times, but I don’t know what this type of method is called, so my searches ended up useless, nor can I explain it to the search engine.

How do you make a method that uses the variable it is appended to as it’s parameter (like “myVariable**.ToString()**)?”

.ToString() works on any variable I append it to, and uses the variable behind it as a parameter, rather than entering the parameter within the brackets… An example of what I want to do would be:

    private void OpenExcel(string inFileName)
    {
        Excel.Application xlApp = new Excel.ApplicationClass();
        Excel.Workbook xlBook = xlApp.Workbooks.Open(inFileName
            , 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);
        Excel.Worksheet xlSheet = (Excel.Worksheet)xlBook.Worksheets[1];

        xlApp.Quit();
        xlApp.releaseObject();
    }

    private void releaseObject(object obj)
    {
        try
        {
            System.Runtime.InteropServices.Marshal.ReleaseComObject(obj);
            obj = null;
        }
        catch (Exception)
        {
            obj = null;
        }
        finally
        {
            GC.Collect();
        }
    }

I know this is kind of a stupid example, but it shows what I want to do with the “xlApp.releaseObject()”.

Also… Can someone please tell me what that kind of method (or type of call, whatever it is) is called? I hate not knowing.

Answer 1

They’re called extension methods and the only two changes that you would need to make to your method are to make it static and to add the keyword this to inFilename:

private static void OpenExcel(this string inFileName)
{
     ...
}

The rest is compiler magic.