Member Avatar for ponkhiraj

Hi, Everybody...
Can anyone knows what is the maximun character limitation of a Label in Vb.net?
Basically i need to scroll a label with timer as Marquee.
The label text is coming from a richtextbox. The richtextbox contains more than billions character.
I replaced all vbLf(LineFeed) of richtextbox with a " * " for getting all character to one line.

But i'm not sure if it will work for label?

Have there any limitation for Label with maximun Character?
Anybody knows?

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  • Latest Post Latest Post by tinstaafl

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Quick practical note for and others: trying to load "billions" of characters into a Label is not practical. In theory a .NET string's length uses a 32‑bit count, but in real apps you'll hit memory, CLR object-size and rendering limits long before that. Letting a Label.AutoSize expand to a huge Width can overflow control coordinates or make the UI unusably slow. A Label is fine for the visible window, but not as storage for an enormous single string.

A robust pattern is to never assign the entire source to the control. Keep a small, fixed-size sliding buffer (StringBuilder) that holds only the characters visible on screen plus a little extra, and advance a pixel offset or start index on each tick. Draw that buffer in OnPaint (TextRenderer.DrawText or Graphics.DrawString) rather than repeatedly setting Label.Text — this avoids huge allocations and gives smoother scrolling. Run the app as 64‑bit if you need more address space, and disable AutoSize on any real controls used for clipping.

Example lightweight approach (custom control that maintains a small circular buffer and scrolls by pixels):

Public Class MarqueePanel
    Inherits Panel

    Private _source As String = ""
    Private _buffer As New System.Text.StringBuilder()
    Private _nextIndex As Integer = 0
    Private _offsetPx As Integer = 0
    Private WithEvents _timer As New Timer()

    Public Sub New()
        DoubleBuffered = True
        _timer.Interval = 30
        _timer.Start()
    End Sub

    Public Sub SetSource(s As String)
        _source = If(s, "")
        Dim approxChars = Math.Max(1, Width \ TextRenderer.MeasureText("W", Font).Width)
        Dim initial = Math.Min(approxChars * 2, _source.Length)
        _buffer.Clear()
        If initial > 0 Then _buffer.Append(_source.Substring(0, initial))
        _nextIndex = initial Mod Math.Max(1, _source.Length)
    End Sub

    Protected Overrides Sub OnPaint(e As PaintEventArgs)
        MyBase.OnPaint(e)
        e.Graphics.Clear(BackColor)
        TextRenderer.DrawText(e.Graphics, _buffer.ToString(), Font, New Point(-_offsetPx, (Height - Font.Height) \ 2), ForeColor)
    End Sub

    Private Sub _timer_Tick(sender As Object, e As EventArgs) Handles _timer.Tick
        _offsetPx += 2
        If _offsetPx >= TextRenderer.MeasureText("W", Font).Width Then
            _offsetPx = 0
            If _source.Length > 0 Then
                _buffer.Remove(0, 1)
                _buffer.Append(_source(_nextIndex))
                _nextIndex = (_nextIndex + 1) Mod _source.Length
            End If
        End If
        Invalidate()
    End Sub
End Class

Troubleshooting tips: enable DoubleBuffered, measure text width to pick buffer size, avoid repeated Substring allocations (use StringBuilder or streaming), and if the source is truly huge read it from disk/stream rather than keeping it all in memory. This approach is much more reliable and performant than trying to shove the whole text into a Label.

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Member Avatar for Begginnerdev

A label does not have a MaxLength Property, but it would probably be safe assumtion that it's a 32bit integer number.

So a label would have 2^32 maximum characters. (4294967296 possible characters)

EDIT

Here is a link that leads to an article with a custom marquee control.

Edited by Begginnerdev
Member Avatar for tinstaafl

actually if your scrolling the info you only need to display whatever will fit in the label; you keep adding character(s)on one end and subtracting character(s) from the other end, the number of characters and the speed with which you add and subtract will determine the speed of the scrolling.

Member Avatar for ponkhiraj

actually if your scrolling the info you only need to display whatever will fit in the label; you keep adding character(s)on one end and subtracting character(s) from the other end, the number of characters and the speed with which you add and subtract will determine the speed of the scrolling.

Dear tinstaafl, can you plz give me an idea on it? Plz if possible submit some code regarding this. I cant get any idea what you want to say.

Member Avatar for tinstaafl

Here's a simple marquee the label starts with the letters of the alphabet and scrolls slow enough your can read them. Iused a button to start it, and it runs for 1 minute. I didn't take the time to use timers, but I'm sure it could be done.

Public Class Form1
    Dim Marquis As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim StartTime, Endtime As Date
        Dim Counter As Integer
        StartTime = Now
        Endtime = StartTime.AddSeconds(60)
        Counter = 0
        While Endtime > Now
            'use Marquis.Chars(Counter) + label1.Text.Substring(0,Label1.Text.Length-1) to reverse direction
            Label1.Text = Label1.Text.Substring(1) + Marquis.Chars(Counter)
            Label1.Refresh()
            'Timer loop
            For I = 1 To 30000000
            Next
            Counter = Counter + 1
            'start over when you get to the end of Marquis
            If Counter > Marquis.Length - 1 Then
                Counter = 0
            End If
        End While

    End Sub
End Class
Edited by tinstaafl
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