RichTextBox: fixed bug when using custom formatter and binding to null/empty text property. Also added RichTextBox.Clear method to allow user to programmatically clear the contents of the RTB.

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/RichTextBox/Formatters/RtfFormatter.cs

@@ -23,10 +23,26 @@ namespace Microsoft.Windows.Controls
 
         public void SetText(FlowDocument document, string text)
         {
-            TextRange tr = new TextRange(document.ContentStart, document.ContentEnd);
-            using (MemoryStream ms = new MemoryStream(Encoding.ASCII.GetBytes(text)))
+            try
+            {
+                //if the text is null/empty clear the contents of the RTB. If you were to pass a null/empty string
+                //to the TextRange.Load method an exception would occur.
+                if (String.IsNullOrEmpty(text))
+                {
+                    document.Blocks.Clear();
+                }
+                else
+                {
+                    TextRange tr = new TextRange(document.ContentStart, document.ContentEnd);
+                    using (MemoryStream ms = new MemoryStream(Encoding.ASCII.GetBytes(text)))
+                    {
+                        tr.Load(ms, DataFormats.Rtf);
+                    }
+                }
+            }
+            catch
             {
-                tr.Load(ms, DataFormats.Rtf);
+                throw new InvalidDataException("Data provided is not in the correct RTF format.");
             }
         }
     }

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/RichTextBox/Formatters/XamlFormatter.cs

@@ -25,15 +25,24 @@ namespace Microsoft.Windows.Controls
         {
             try
             {
-                TextRange tr = new TextRange(document.ContentStart, document.ContentEnd);
-                using (MemoryStream ms = new MemoryStream(Encoding.ASCII.GetBytes(text)))
+                //if the text is null/empty clear the contents of the RTB. If you were to pass a null/empty string
+                //to the TextRange.Load method an exception would occur.
+                if (String.IsNullOrEmpty(text))
                 {
-                    tr.Load(ms, DataFormats.Xaml);
+                    document.Blocks.Clear();
+                }
+                else
+                {
+                    TextRange tr = new TextRange(document.ContentStart, document.ContentEnd);
+                    using (MemoryStream ms = new MemoryStream(Encoding.ASCII.GetBytes(text)))
+                    {
+                        tr.Load(ms, DataFormats.Xaml);
+                    }
                 }
             }
             catch
             {
-                throw new InvalidDataException("data provided is not in the correct Xaml format.");
+                throw new InvalidDataException("Data provided is not in the correct Xaml format.");
             }
         }
     }

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/RichTextBox/RichTextBox.cs

@@ -95,6 +95,14 @@ namespace Microsoft.Windows.Controls
             _textSetInternally = false;
         }
 
+        /// <summary>
+        /// Clears the content of the RichTextBox.
+        /// </summary>
+        public void Clear()
+        {
+            Document.Blocks.Clear();
+        }
+
         #endregion //Methods
 
         #region Event Hanlders