Question

I’m creating a chat app in Windows 8 Windows Metro Style App. I need to append the conversation in a richtextblock or textblock in XAML. Would somebody tell me the equivalent for this Code block?

public void AppendConversation(string str)
{
    conversation.Append(str);
    rtbConversation.Text = conversation.ToString();
    rtbConversation.Focus();
    rtbConversation.SelectionStart = rtbConversation.Text.Length - 1;
    rtbConversation.ScrollToCaret();
    rtbSendMessage.Focus();
}

Answer 1

Since WPF uses System.Windows.Controls instead of System.Windows.Forms, we must consider the following

1. System.Windows.Controls.RichTextBox does not have a property for Text to set its value, we may set its value creating a new class of TextRange since the control depends on TextPointer which can be defined using TextRange

string _Text = ""
new TextRange(
  rtbConversation.Document.ContentStart,
  rtbConversation.Document.ContentEnd).Text = _Text;

---

2. Selections in System.Windows.Controls.RichTextBox does not depend on int yet they are held by TextPointer. So, we can’t say

rtbConversation.SelectionStart = rtbConversation.Text.Length - 1;

but we can say

int TextLength = new TextRange(
  rtbConversation.Document.ContentStart,
  rtbConversation.Document.ContentEnd).Text.Length;
TextPointer tr = rtbConversation.Document.ContentStart.GetPositionAtOffset(
  TextLength - 1, LogicalDirection.Forward);
rtbConversation.Selection.Select(tr, tr);

which will do the same as rtbConversation.SelectionStart = rtbConversation.Text.Length - 1;

Remark: You can always retrieve the beginning of the selection in WPF using RichTextBox.Selection.Start

Notice: RichTextBox.Selection.Start outputs a class of name TextPointer but not a struct of name int

---

3. Finally, System.Windows.Controls.RichTextBox does not have a definition for ScrollToCaret();. In this case, we may use one of the following voids regarding your control rtbConversation

rtbConversation.ScrollToEnd();
rtbConversation.ScrollToHome();
rtbConversation.ScrollToHorizontalOffset(double offset);
rtbConversation.ScrollToVerticalOffset(double offset);

---

So, your void should look like this in WPF

Example

public void AppendConversation(string str)
{   
    conversation.Append(str) // Sorry, I was unable to detect the type of 'conversation'
    new TextRange(rtbConversation.Document.ContentStart,
                  rtbConversation.Document.ContentEnd).Text =
                    conversation.ToString();
    rtbConversation.Focus();
    int TextLength = new TextRange(rtbConversation.Document.ContentStart,
                                   rtbConversation.Document.ContentEnd).Text.Length;
    TextPointer tr = rtbConversation.Document.ContentStart.GetPositionAtOffset(
        TextLength - 1, LogicalDirection.Forward);
    rtbConversation.Selection.Select(tr, tr);
    rtbConversation.ScrollToEnd();
    rtbSendMessage.Focus();
}

Thanks,

I hope you find this helpful 🙂