Below is a c# code whose purpose is to append an image to a .rtf file that already has text image. When i run the code, i get the error that says “Error: File format is not valid”.
Program.cs code

static void Main(string[] args)
        {
        
        FileStreamWriter fileStreamWriter = new FileStreamWriter();
        fileStreamWriter.StreamWriterThing();
        FileStreamWriter.AddImageToRTF("Text3.rtf","demo.bmp");
        Console.ReadLine();
        }
}

FileStreamWriter.cs file code

public void StreamWriterThing()
 {
     
         FileStream fs2 = new FileStream("Text3.rtf", FileMode.OpenOrCreate, 
FileAccess.Write);
         StreamWriter sr1 = new StreamWriter(fs2);
         sr1.WriteLine("n" + "Writing data into file using stream writer");
         sr1.Close();
         fs2.Close();
         string Fdata;
         FileStream fs3 = new FileStream("Text3.rtf", FileMode.OpenOrCreate, 
         FileAccess.Read);
         using (StreamReader sr2 = new StreamReader(fs3))
         {
             Fdata = sr2.ReadToEnd();
             sr2.Close();
         }
         Console.WriteLine(Fdata);
         fs3.Close();
     }

 

public static void AddImageToRTF(string rtfFilePath, string imagePath)
 {
     try
     {
         // Load existing RTF content
         RichTextBox richTextBox = new RichTextBox();
         richTextBox.LoadFile(rtfFilePath);

         // Load the image from the file
         Image image = Image.FromFile(imagePath);

         // Create a valid RTF template with the image placeholder
         string rtfTemplate = $@"{{rtf1ansideff0{{*imageresolution 96}} 
{{*pngblip{{*name Image1 *filename ""{imagePath}"" *flags 0 *tx 0 *ty 0 
*w 0 *h 0}}}}}}";

         // Set the RTF content to the template
         richTextBox.SelectedRtf = rtfTemplate;

         // Save the modified RTF back to the file
         richTextBox.SaveFile(rtfFilePath, RichTextBoxStreamType.RichText);

         Console.WriteLine("Image successfully added to RTF.");
     }
     catch (Exception ex)
     {
         Console.WriteLine($"Error: {ex.Message}");
     }
 }

Where could i be going wrong?