Question

What is the best way to detect if a WPF RichTextBox/FlowDocument is empty?

The following works if only text is present in the document. Not if it contains UIElement’s

new TextRange(Document.ContentStart, Document.ContentEnd).IsEmpty

Answer 1

You could compare the pointers, which is not all too reliable:

var start = rtb.Document.ContentStart;
var end = rtb.Document.ContentEnd;
int difference = start.GetOffsetToPosition(end);

This evaluates to 2 if the RTB is loaded, and 4 if content has been entered and removed again.
If the RTB is completely cleared out e.g. via select all -> delete the value will be 0.

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In the Silverlight reference on MSDN another method is found which can be adapted and improved to:

public bool IsRichTextBoxEmpty(RichTextBox rtb)
{
    if (rtb.Document.Blocks.Count == 0) return true;
    TextPointer startPointer = rtb.Document.ContentStart.GetNextInsertionPosition(LogicalDirection.Forward);
    TextPointer endPointer = rtb.Document.ContentEnd.GetNextInsertionPosition(LogicalDirection.Backward);
    return startPointer.CompareTo(endPointer) == 0;
}