RichTextBox Newline Conversion?

Question

I'm using a WinForms RichTextBox. It appears that when the RichTextBox is on a form, \r\n gets converted to \n. Here's a test:

I have two rich text boxes. One is richTextBox1, which is placed on the form:

  this.richTextBox1 = new System.Windows.Forms.RichTextBox();
  this.SuspendLayout();
  // 
  // richTextBox1
  // 
  this.richTextBox1.Location = new System.Drawing.Point(37, 12);
  this.richTextBox1.Name = "richTextBox1";
  this.richTextBox1.Size = new System.Drawing.Size(100, 96);
  this.richTextBox1.TabIndex = 0;
  this.richTextBox1.Text = "";

The other is rtb, which I create on the spot. When I run this code (in the form's load event):

  var rtb = new RichTextBox();
  string enl = "Cheese" + Environment.NewLine + "Whiz";
  rtb.Text = enl;
  string ncr = rtb.Text;
  MessageBox.Show(string.Format("{0}{1}{2}{3}---{4}{5}{6}{7}{8}{9}",
                                enl.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                ncr.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                Environment.NewLine,
                                (enl == ncr), Environment.NewLine,
                                enl.Contains(Environment.NewLine), Environment.NewLine,
                                ncr.Contains(Environment.NewLine)));
  /*
  Cheese\r\nWhiz
  Cheese\r\nWhiz
  ---
  True
  True
  True
  */
  richTextBox1.Text = enl;
  string ncr2 = richTextBox1.Text;
  MessageBox.Show(string.Format("{0}{1}{2}{3}---{4}{5}{6}{7}{8}{9}",
                                enl.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                ncr2.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                Environment.NewLine,
                                (enl == ncr2), Environment.NewLine,
                                enl.Contains(Environment.NewLine), Environment.NewLine,
                                ncr2.Contains(Environment.NewLine)));
  /*
  Cheese\r\nWhiz
  Cheese\nWhiz
  ---
  False
  True
  False
  */

The RichTextBox seems to be exhibiting some strange behavior. When I put text containing a \r\n into the box I just created, it stays the same (still contains the \r\n). However, when I put text containing an \r\n into the box on the form, the \r\n gets turned into \n.

My Questions: Is there a reason for this behavior (\r\n->\n)? Is this behavior documented somewhere? Can I count on it always being this way?

The case I posted here is my attempt at getting to the bottom of a problem I've been having with one of my forms in a different project, so I'd appreciate any input regarding this issue.

Answer 1

The RichTextBox.Text property is converting the assigned string into an rtf document according to the Rtf format codes specified in the RichTextBox.Rtf property. Since the 'rtb' instance is not being initialized the 'Rtf' format codes are empty, and it's just echoing back your input. After 'rtb' is initialized it contains an empty rtf document (with format codes), which is the same (and correct) behavior as 'richTextBox1'.

Results:

preinit  rtb.Rtf : ''
postinit rtb.Rtf : '"{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil\\fcharset0 Microsoft Sans Serif;}}\r\n\\viewkind4\\uc1\\pard\\f0\\fs17\\par\r\n}\r\n"'
richTextBox1.Rtf : '"{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil\\fcharset0 Microsoft Sans Serif;}}\r\n\\viewkind4\\uc1\\pard\\f0\\fs17\\par\r\n}\r\n"'
richtextBox1.Rtf with cheese : '"{\\rtf1\\ansi\\deff0{\\fonttbl{\\f0\\fnil\\fcharset0 Microsoft Sans Serif;}}\r\n\\viewkind4\\uc1\\pard\\lang1033\\f0\\fs17 Cheese\\par\r\nWhiz\\par\r\n}\r\n"'

Code:

void Form1_Load(object sender, EventArgs e)
{
    TestIt();
}
public void TestIt()
{
    string enl = "Cheese" + Environment.NewLine + "Whiz";

    RichTextBox rtb = new RichTextBox();
    MessageBox.Show("preinit rtb.Rtf : '" + rtb.Rtf + "'");
    this.Controls.Add(rtb);
    MessageBox.Show("postinit rtb.Rtf : '" + rtb.Rtf + "'");
    MessageBox.Show("richTextBox1.Rtf : '" + richTextBox1.Rtf + "'");

    rtb.Text = enl;
    string ncr = rtb.Text;
    MessageBox.Show(string.Format("rtb: {0}{1}{2}{3}---{4}{5}{6}{7}{8}{9}",
                                  enl.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                  ncr.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                  Environment.NewLine,
                                  (enl == ncr), Environment.NewLine,
                                  enl.Contains(Environment.NewLine), Environment.NewLine,
                                  ncr.Contains(Environment.NewLine)));
    /*
    Cheese\r\nWhiz
    Cheese\nWhiz
    ---
    False
    True
    False
    */
    richTextBox1.Text = enl;
    MessageBox.Show("richTextBox1.Rtf with cheese : '" + richTextBox1.Rtf + "'");
    string ncr2 = richTextBox1.Text;
    MessageBox.Show(string.Format("richTextBox1: {0}{1}{2}{3}---{4}{5}{6}{7}{8}{9}",
                                  enl.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                  ncr2.Replace("\n", "\\n").Replace("\r", "\\r"), Environment.NewLine,
                                  Environment.NewLine,
                                  (enl == ncr2), Environment.NewLine,
                                  enl.Contains(Environment.NewLine), Environment.NewLine,
                                  ncr2.Contains(Environment.NewLine)));
    /*
    Cheese\r\nWhiz
    Cheese\nWhiz
    ---
    False
    True
    False
    */
}

Answer 2

  var rtb = new RichTextBox();
  string enl = "Cheese" + Environment.NewLine + "Whiz";
  rtb.Text = enl;

This is a side-effect of the way the Text property works. It is cached in Control.Text, the actual native Windows control doesn't get updated until it is created. Problem is, that never happened with your rtb. You didn't add it to a form so the native control did not get created. Typical lazy resource allocation pattern in .NET. Consequently, you are reading the cached value, not the value from the control.

To see this, modify the code to force the control to be created:

        var rtb = new RichTextBox();
        rtb.CreateControl();
        string enl = "Cheese" + Environment.NewLine + "Whiz";
        rtb.Text = enl;

And you'll see that \r\n now is translated to \n. Don't forget to Dispose() the control.