Opening a xls spreadsheet programatically in C# from a SharePoint site in Read / Write mode

Question

I have written a procedure that will open a xls from a local disc, refresh the data in it and then save it again. This works fine.

The problem occurs when I replace the filename to point to a SharePoint site. It opens the file fine. Refreshes the file, but when it trys to save the file it throws an exception with the message "Cannot save as that name. Document was opened as read-only.". If I try and save the file with a different filename then it works fine.

Does anybody know what I am missing? I think it must have somethoing to do with how I am opening the file. Is there another way that I can force the opening of the file in a read/write manner?

    private static void RefreshExcelDocument(string filename)
    {
        var xls = new Microsoft.Office.Interop.Excel.Application();
        xls.Visible = true;
        xls.DisplayAlerts = false;
        var workbook = xls.Workbooks.Open(Filename: filename, IgnoreReadOnlyRecommended: true, ReadOnly: false);
        try
        {
            // Refresh the data from data connections
            workbook.RefreshAll();
            // Wait for the refresh occurs - *wish there was a better way than this.
            System.Threading.Thread.Sleep(5000);
            // Save the workbook back again
            workbook.SaveAs(Filename: filename);  // This is when the Exception is thrown
            // Close the workbook
            workbook.Close(SaveChanges: false);
        }
        catch (Exception ex)
        {
            //Exception message is "Cannot save as that name. Document was opened as read-only."
        }
        finally
        {

            xls.Application.Quit();
            xls = null;
        }
    }

Many thanks in advance for suggestions.

Jonathan

Answer 1

Unfortunately you can't save directly to SharePoint using the Excel API. That's why the file is being opened as read only - it's not allowed.

The good news is that it is possible, but you have to submit the form via a web request. Even better news is that there is sample code on MSDN! In particular notice the PublishWorkbook method that sends a local copy of the Excel file to the server via a web request:

static void PublishWorkbook(string LocalPath, string SharePointPath)
{
    WebResponse response = null;

    try
    {
        // Create a PUT Web request to upload the file.
        WebRequest request = WebRequest.Create(SharePointPath);

        request.Credentials = CredentialCache.DefaultCredentials;
        request.Method = "PUT";

        // Allocate a 1K buffer to transfer the file contents.
        // The buffer size can be adjusted as needed depending on
        // the number and size of files being uploaded.
        byte[] buffer = new byte[1024];

        // Write the contents of the local file to the
        // request stream.
        using (Stream stream = request.GetRequestStream())
        using (FileStream fsWorkbook = File.Open(LocalPath,
            FileMode.Open, FileAccess.Read))
        {
            int i = fsWorkbook.Read(buffer, 0, buffer.Length);

            while (i > 0)
            {
                stream.Write(buffer, 0, i);
                i = fsWorkbook.Read(buffer, 0, buffer.Length);
            }
        }

        // Make the PUT request.
        response = request.GetResponse();
    }
    finally
    {
        response.Close();
    }
}

The sample code describes a scenario for the 2007 versions of these products but other versions should behave in the same way.

Answer 2

What does the filename of a failed example looks like? Aren't documents used in SharePoint stored in the database? Or am I getting your problem wrong? Otherwise I could imagine that the file you are trying to store is write protected by the operation system and cannot be modified.