Update progressbar + clipboard.getimage() with backgroundworker - WPF C#

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C#

WPF

Hello

my program should export certain Excel files from a folder as an image (in SVG format) into another folder. This can be done by the Methods CopyAndSaveTo and ExportRangeAsImage and they do their job.
On the MainWindow I have a button that performs these two functions when it is clicked. I want the User who clicks on this button be informed (Progressbar) how far is this process (Copy + export).
I have tried to realise it using a BackgroundWorker and it works only if I comment the following code (in the Method ExportRangeAsImage):

Bitmap image = new Bitmap(System.Windows.Forms.Clipboard.GetImage());
image.Save(ImagePath + Path.GetFileNameWithoutExtension(file) + ".svg");

Otherwise I get the following error message (
translated from German):

In System.NullReferenceException an exception of type "System.Drawing.dll" has occurred, but was this not processed in the user code.

Additional information: Object reference not set to an object instance.

If a handler is available for this exception, the program may continue to run safely.


Here is the whole code:

private void UpdateDataOfLine1(object sender, ExecutedRoutedEventArgs e)
        {
            string[] files = Directory.GetFiles(RootPath);

            BackgroundWorker worker = new BackgroundWorker();
            worker.WorkerReportsProgress = true;
            worker.DoWork += worker_DoWork;
            worker.ProgressChanged += worker_ProgressChanged;
            worker.RunWorkerAsync();
        }



        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            string[] files = Directory.GetFiles(RootPath);

            for (int i = 0; i < files.Length; i++)
            {
                if (files[i].Contains("$") || files[i].Contains("~") || files[i].Contains("Thumb"))
                {
                    continue;
                }

                File.Copy(files[i], DestPath + Path.GetFileName(files[i]), true);

                string newFile = DestPath + Path.GetFileName(files[i]);

                ExPortRangeAsImage(newFile);

                (sender as BackgroundWorker).ReportProgress(i);
                Thread.Sleep(100);
            }
        }



        void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            Status.Value = e.ProgressPercentage;
        }


        public void ExPortRangeAsImage(string file)
        {
            var ExcelApp = new Microsoft.Office.Interop.Excel.Application();

            try
            {
                if (file.Contains("BeispielDatei"))
                {
                    Workbook wb = ExcelApp.Workbooks.Open(file);
                    Worksheet ws = (Worksheet)wb.Sheets[1];
                    Range range = ws.Range["A1:U35"];
                    range.CopyPicture(XlPictureAppearance.xlScreen, XlCopyPictureFormat.xlBitmap);
                    wb.Close(SaveChanges: false);
                    Marshal.ReleaseComObject(wb);
                }

                else
                {
                    Workbook wb = ExcelApp.Workbooks.Open(file);
                    Worksheet ws = (Worksheet)wb.Sheets[1];
                    Range range = ws.Range["A1:U35"];
                    range.CopyPicture(XlPictureAppearance.xlScreen, XlCopyPictureFormat.xlBitmap);
                    wb.Close(SaveChanges: false);
                    Marshal.ReleaseComObject(wb);
                }
            }

            finally
            {
                Bitmap image = new Bitmap(System.Windows.Forms.Clipboard.GetImage());
                image.Save(ImagePath + Path.GetFileNameWithoutExtension(file) + ".svg");

                Marshal.ReleaseComObject(ExcelApp);
            }
        }

What I have tried:

private void UpdateDataOfLine1(object sender, ExecutedRoutedEventArgs e)
        {
            string[] files = Directory.GetFiles(RootPath);

            BackgroundWorker worker = new BackgroundWorker();
            worker.WorkerReportsProgress = true;
            worker.DoWork += worker_DoWork;
            worker.ProgressChanged += worker_ProgressChanged;
            worker.RunWorkerAsync();
        }



        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            string[] files = Directory.GetFiles(RootPath);

            for (int i = 0; i < files.Length; i++)
            {
                if (files[i].Contains("$") || files[i].Contains("~") || files[i].Contains("Thumb"))
                {
                    continue;
                }

                File.Copy(files[i], DestPath + Path.GetFileName(files[i]), true);

                string newFile = DestPath + Path.GetFileName(files[i]);

                ExPortRangeAsImage(newFile);

                (sender as BackgroundWorker).ReportProgress(i);
                Thread.Sleep(100);
            }
        }



        void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            Status.Value = e.ProgressPercentage;
        }


        public void ExPortRangeAsImage(string file)
        {
            var ExcelApp = new Microsoft.Office.Interop.Excel.Application();

            try
            {
                if (file.Contains("BeispielDatei"))
                {
                    Workbook wb = ExcelApp.Workbooks.Open(file);
                    Worksheet ws = (Worksheet)wb.Sheets[1];
                    Range range = ws.Range["A1:U35"];
                    range.CopyPicture(XlPictureAppearance.xlScreen, XlCopyPictureFormat.xlBitmap);
                    wb.Close(SaveChanges: false);
                    Marshal.ReleaseComObject(wb);
                }

                else
                {
                    Workbook wb = ExcelApp.Workbooks.Open(file);
                    Worksheet ws = (Worksheet)wb.Sheets[1];
                    Range range = ws.Range["A1:U35"];
                    range.CopyPicture(XlPictureAppearance.xlScreen, XlCopyPictureFormat.xlBitmap);
                    wb.Close(SaveChanges: false);
                    Marshal.ReleaseComObject(wb);
                }
            }

            finally
            {
                Bitmap image = new Bitmap(System.Windows.Forms.Clipboard.GetImage());
                image.Save(ImagePath + Path.GetFileNameWithoutExtension(file) + ".svg");

                Marshal.ReleaseComObject(ExcelApp);
            }
        }

Can you show me what I'm doing wrong or how I can realize it?
Are there other ways than BackgroundWorker?

Thank you in advance for your help!