C# Edit image Exif using XMP from Adobe

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C#

Windows

Win7

image

I'm working in a small project, that his major role is to edit the Metadata of an "jpg" image file, I'm using C# as a primary language. I did some research and I found about XMP from Adobe, I downloaded XMP toolkit dll file supporting C#

this is a small example for the code I'm trying to do:

string filepath = @"C:\image.jpg";
void EditImage()
{
    try
    {
        using (Xmp xmp = Xmp.FromFile(filePath, XmpFileMode.ReadWrite))
        {

            string xmpDump = xmp.Dump();
            editdata(xmp);
            xmpDump = xmp.Dump();
            xmp.Save();


        }
    }
    catch (Exception e)
    {
        MessageBox.Show(e.Message);
    }
}
string Title = textbox1.Text;
string keywords = textbox2.Text;
void editdata(Xmp xmp)
{

    DublinCore dc = new DublinCore(xmp);
    dc.Subject.Clear();
    string[] keyword = keywords.Split('-');

    foreach (string item in keyword)
    {
        dc.Subject.Add(item);
    }

    dc.Title.Clear();
    dc.Title.DefaultValue = Title;
    dc.Description.Clear();
    dc.Description.DefaultValue = "Some description";
}

the Program goal is to edit the image Metadata to support Arabic language
what I'm trying yo do in this code is working perfectly, except when I want to add the description, this is an example for the tag -keyword- of the picture when I use the program:
"واحد; ????; ", this tag will be showing in the properites - details of the picture using windows 7.

Thank you for any help.

Best,