Limit Number of Lines in TextBox

[jseal]

Hi, how do I limit the number of lines in a multiline textbox? I don't want to limit the characters, just the number of lines.

[jmcilhinney]

Handle the KeyDown event and trap the Enter key. Count the number of lines currently in the control and if it's already at the maximum then set e.SuppressKeyPress to True.

[jseal]

Could I possibly get a code example of how this is done?

Thanks

[jmcilhinney]

Private Const MAX_LINE_COUNT As Integer = 10 'for example
 
Private Sub TextBox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
    If e.KeyCode = Keys.Enter Then
        e.SuppressKeyPress = (Me.TextBox1.Lines.Length >= MAX_LINE_COUNT)
    End If
End Sub

[sevenhalo]

That works so long as wordwrapping is disabled.

Private Const MaxLines As Int32 = 3
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        dim hold As TextBox = DirectCast(sender, TextBox)
            If hold.GetPositionFromCharIndex(hold.Text.Length - 1).Y > (MaxLines * hold.Font.Height) Then
                hold.Text = hold.Text.Remove(hold.Text.Length - 1)
                hold.SelectionStart = hold.Text.Length
            End If
    End Sub

If you can find a way to get keyup's e.surpresskeypress to work properly (it's in the arg, just doesn't stop anything); there's a much cleaner way. Otherwise, this will work as long as the lines your textbox is displaying is greater or equal to the number of lines you're capping.

Edit: changed a me.textbox1 to hold

[jmcilhinney]

Given that the KeyPress event is raised before the KeyUp event, there isn't anything to suppress. KeyDown and KeyUp both receive a KeyEventArgs object but the SuppressKeyPress was added specifically for the KeyDown event and is only useful for that event.

Also, you DEFINITELY don't want to have a Using block like that in your event handler. The purpose of a Using block is to ensure that the object referred to by the variable declared in the Using statement gets disposed at the end of the block. I very much doubt that you want to dispose a TextBox in its own TextChanged event handler.

[sevenhalo]

Also, you DEFINITELY don't want to have a Using block like that in your event handler. The purpose of a Using block is to ensure that the object referred to by the variable declared in the Using statement gets disposed at the end of the block. I very much doubt that you want to dispose a TextBox in its own TextChanged event handler.

Haha, I was just about to fix that. I forgot I didn't insantiate the object.