Silverlight RichtTextBox ContentStart & ContentEnd

On the MSDN site, I开发者_StackOverflow found a method, which checks to see if a Silverlight RichTextBox usercontrol is empty or not.

Link: http://msdn.microsoft.com/en-us/library/system.windows.controls.richtextbox.contentstart%28v=vs.95%29.aspx

Method:

public bool isRichTextBoxEmpty()
{
    TextPointer startPointer = myRichTextBox.ContentStart.GetNextInsertionPosition(LogicalDirection.Forward);
    TextPointer endPointer = myRichTextBox.ContentEnd.GetNextInsertionPosition(LogicalDirection.Backward);
    if (startPointer.CompareTo(endPointer) == 0) {
        return true;
    }
    else {
        return false;
    }
}

However, if the RichTextBox is actually empty, this crashes the Silverlight App. No TextPointers were returned and thus the 2 variables are filled with null.

What I did to clear the RichTextBox is use a button which executes this:

if(!isRichTextBoxEmpty()) {
    myRichTextBox.Blocks.Clear();
}

With that exact function. So if there is text, it does work. If there is non, I get null-references. What is happening here?

Working in Silverlight 4.0

You need at least one block for the method to work.

I would add the following line at the beginning of the method:

if (myRichTextBox.Blocks.Count == 0) return true;

The method in its original form is not safe, it's even rather redundant as it uses

if (startPointer.CompareTo(endPointer) == 0)
    return true;
else
    return false;

instead of

return startPointer.CompareTo(endPointer) == 0;

(The camelCase method name seems fishy to me as well)