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  xlWorkBook = xlApp.Workbooks.Add(misValue);                    

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xlApp = new Excel.Application(); // anstatt ApplicationClass()                    

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Excel.Application myExcelApplication;
            Excel.Workbook myExcelWorkbook;
            Excel.Worksheet myExcelWorkSheet;
            myExcelApplication = null; 

            try
            {
                // First Contact: Excel Prozess initialisieren
                myExcelApplication = new Excel.Application();
                myExcelApplication.Visible = true; // hier kommt der fehler, mit der nicht registrierten bibliothek
                myExcelApplication.ScreenUpdating = true;

                // Excel Datei anlegen: Workbook
                var myCount = myExcelApplication.Workbooks.Count;
                myExcelWorkbook = (Excel.Workbook)(myExcelApplication.Workbooks.Add(System.Reflection.Missing.Value));
                myExcelWorkSheet = (Excel.Worksheet)myExcelWorkbook.ActiveSheet;

               
                // Excel Datei abspeichern
                // wenn die Datei vorher vorhanden ist, kommt in Excel eine Fehlermeldung.
                myExcelWorkbook.Close(true, "C:\\kunden.xls", System.Reflection.Missing.Value);
            }

            catch (Exception ex)
            {
                String myErrorString = ex.Message;
                MessageBox.Show(myErrorString);
            }
            finally
            {
                // Excel beenden
                if (myExcelApplication != null)
                {
                    myExcelApplication.Quit();
                }

            }                    

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C:\Windows\System32\URTTemp\Regtlib.exe "C:\Programme\Microsoft Office\Office10\Excel10.OLB"