Converting from rich text format to plain text pro

Question

We currently have an application (Windows service) that connects to another of our applications and grabs invoices. In the invoices there is a RTF field for the footer/header fields. When we grab the data the RTF is converted to plain text with the following code:

public static string ConvertFromRTFToPlainText(string rtfString)
{
    if (rtfString == null)
        return null; 

    System.Windows.Forms.RichTextBox rtBox = new System.Windows.Forms.RichTextBox();

    if (rtfString.StartsWith("{\\rtf1"))
        rtBox.Rtf = rtfString;
    else
        rtBox.Text = rtfString;

    return rtBox.Text;
}

This has worked for the most part but in some cases (one particular client gets it everytime) I get this exception:

Exception Message:Error creating window handle.
Stack trace:
at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp)
at System.Windows.Forms.Control.CreateHandle()
at System.Windows.Forms.TextBoxBase.CreateHandle()
at System.Windows.Forms.RichTextBox.set_Rtf(String value)
at SmartTrade.Common.API.Tools.RTFHelperUtility.ConvertFromRTFToPlainText(String rtfString)
at SmartTrade.Desktop.Proxy.API.ObjectMapper.InvoiceObjectMapper.CovertToAPIInvoice(Invoice domainInvoice)

Any help on why this is happening or how we can work around it would be much appreciated.

Edit: Thanks to Jeremy for the explanation, I am after suggestions for RTF conversion alternatives.

Answer 1

I ended up using this. I know that it may not parse 100% of RTF text but we ran it against our live data to test it and it works fine for our purposes.

Regex.Replace(rtfString, @"\{\*?\\[^{}]+}|[{}]|\\\n?[A-Za-z]+\n?(?:-?\d+)?[ ]?", "");

Answer 2

I would say this is probably thrown on terminal type machines that don't have the UI libraries installed? Or possibly don't have them loaded (ie - if no user is logged in)

It's generally not a great idea to use UI libraries in a service, because there is no guarantee that those libraries are accessible if no user is logged in.

I would find a different way to remove the RTF formatting