I need to limit the number of characters to be pasted in a multiline textbox.
Let's say this is my string to be pasted in the textbox:
Good day Ladies and Gents!
I just want to know
If this is possible, please help.
The rule is maximum characters PER LINE is 10, Maximum ROWS is 2. Applying the rule, pasted text should only be like this:
Good day L
I just wan
There is not automatic what to do this. You'll need to handle the TextChanged event on the text box and manually parse the changed text to limit it to the format required.
private const int MaxCharsPerRow = 10; private const int MaxLines = 2; private void textBox1_TextChanged(object sender, EventArgs e) { string[] lines = textBox1.Lines; var newLines = new List<string>(); for (int i = 0; i < lines.Length && i < MaxLines; i++) { newLines.Add(lines[i].Substring(0, Math.Min(lines[i].Length, MaxCharsPerRow))); } textBox1.Lines = newLines.ToArray(); } You can catch the message WM_PASTE (sent to your TextBox) to process yourself:
public class MyTextBox : TextBox { int maxLine = 2; int maxChars = 10; protected override void WndProc(ref Message m) { if (m.Msg == 0x302)//WM_PASTE { string s = Clipboard.GetText(); string[] lines = s.Split('\n'); s = ""; int i = 0; foreach (string line in lines) { s += (line.Length > maxChars ? line.Substring(0, maxChars) : line) + "\r\n"; if (++i == maxLine) break; } if(i > 0) SelectedText = s.Substring(0,s.Length - 2);//strip off the last \r\n return; } base.WndProc(ref m); } } 
You can achieve this by the following way. Set maximum length of the text box as 22
textBox1.MaxLength = 22; In the text change event do the following
private void textBox1_TextChanged(object sender, EventArgs e) { if (textBox1.Text.Length == 10) { textBox1.AppendText("\r\n"); } } This will automatically enters to next line after 10 characters
Why dont you work on the clipboard data to achieve this. Below is a small example .
String clipboardText = Clipbard.GetText( ); // MAXPASTELENGTH - max length allowed by your program if(clipboardText.Length > MAXPASTELENGTH) { Clipboard.Clear(); String newClipboardText = clipboardText.Substring(0, MAXPASTELENGTH); // set the new clipboard data to the max length SetData(DataFormats.Text, (Object)newClipboardText ); } Now paste the data whereever you like , the data shall be trimmed to the maximum length allowed by your program .
private void textBox1_TextChanged(object sender, EventArgs e) { if (textBox1.Text.Length == 10) { textBox1.MaxLength = 10; //MessageBox.Show("maksimal 10 karakter"); } } 
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