C# and Excel advanced filter

Question

I'm trying to filter data from one workbook to another obne, but I get an unpsecified exception.

I can't find many examples for adavnced filtering in excel using c# and I don't know Where's exactly my error.

Here's my code:

public void excel()
    {
        Excel.Application xlApp;
        Excel.Workbook xlWorkBookImport;
        Excel.Workbook xlWorkBookOriginal;
        Excel.Worksheet xlWorkSheetImport;
        Excel.Worksheet xlWorkSheetOriginal;

        xlApp = new Excel.ApplicationClass();
        xlWorkBookImport = xlApp.Workbooks.Open("c:/open.xls");
        xlWorkBookOriginal = xlApp.Workbooks.Open("c:/open1.xls");
        xlWorkBookOriginal.Activate();
        xlWorkSheetOriginal = (Excel.Worksheet)xlWorkBookOriginal.Worksheets.get_Item(1);
        xlWorkSheetOriginal.get_Range("1:7").Delete();
        xlWorkBookImport.Activate();
        xlWorkSheetImport = (Excel.Worksheet)xlWorkBookImport.Worksheets.get_Item(1);
        xlWorkSheetOriginal.Cells.AdvancedFilter(Excel.XlFilterAction.xlFilterCopy, Type.Missing, CopyToRange: "a1:a6", Unique: true);

        xlApp.Visible = true;
    }

Anyone can help me with a solution?

Thanks,

Udi