How do I automatically scroll to the bottom of a multiline text box

Question

I have a textbox with the  Multiline property set to true   At regular intervals  I am adding new lines of text to it   I would like the textbox to automatically scroll to the bottom-most entry  the newest one  whenever a new line is added   How do I accomplish this

User · Answer

textBox1 Focus   textBox1 SelectionStart   textBox1 Text Length  textBox1 ScrollToCaret      didn t work for me  Windows 8 1  whatever the reason   And since I m still on  NET 2 0  I can t use ScrollToEnd   But this works   public class Utils        System Runtime InteropServices DllImport  user32 dll   CharSet   System Runtime InteropServices CharSet Auto       private static extern int SendMessage System IntPtr hWnd  int wMsg  System IntPtr wParam  System IntPtr lParam        private const int WM VSCROLL   0x115      private const int SB BOTTOM   7            lt summary gt          Scrolls the vertical scroll bar of a multi-line text box to the bottom           lt  summary gt           lt param name  tb  gt The text box to scroll lt  param gt      public static void ScrollToBottom System Windows Forms TextBox tb                if System Environment OSVersion Platform    System PlatformID Unix               SendMessage tb Handle  WM VSCROLL  new System IntPtr SB BOTTOM   System IntPtr Zero               VB NET   Public Class Utils      lt System Runtime InteropServices DllImport  user32 dll   CharSet    System Runtime InteropServices CharSet Auto  gt        Private Shared Function SendMessage hWnd As System IntPtr  wMsg As Integer  wParam As System IntPtr  lParam As System IntPtr  As Integer     End Function      Private Const WM VSCROLL As Integer    amp H115     Private Const SB BOTTOM As Integer   7           lt summary gt          Scrolls the vertical scroll bar of a multi-line text box to the bottom           lt  summary gt           lt param name  tb  gt The text box to scroll lt  param gt      Public Shared Sub ScrollToBottom tb As System Windows Forms TextBox          If System Environment OSVersion Platform  lt  gt  System PlatformID Unix Then             SendMessage tb Handle  WM VSCROLL  New System IntPtr SB BOTTOM   System IntPtr Zero          End If     End Sub   End Class

User · Answer

You can use the following code snippet   myTextBox SelectionStart   myTextBox Text Length  myTextBox ScrollToCaret      which will automatically scroll to the end

User · Answer

It seems the interface has changed in  NET 4 0   There is the following method that achieves all of the above  As Tommy Engebretsen suggested  putting it in a TextChanged event handler makes it automatic   textBox1 ScrollToEnd

User · Answer

I use a function for this    private void Log  string s        TB1 AppendText Environment NewLine   s       TB1 ScrollToCaret

User · Answer

This only worked for me      txtSerialLogging- Text        txtSerialLogging- AppendText s    I tried all the cases above  but the problem is in my case text s can decrease  increase and can also remain static for a long time  static means   static length lines  but content is different   So  I was facing one line jumping situation at the end when the length lines  remains same for some times

User · Answer

Try to add the suggested code to the TextChanged event   private void textBox1 TextChanged object sender  EventArgs e      textBox1 SelectionStart   textBox1 Text Length    textBox1 ScrollToCaret

User · Answer

At regular intervals  I am adding new lines of text to it  I would like the textbox to automatically scroll to the bottom-most entry  the newest one  whenever a new line is added    If you use TextBox AppendText string text   it will automatically scroll to the end of the newly appended text  It avoids the flickering scrollbar if you re calling it in a loop   It also happens to be an order of magnitude faster than concatenating onto the  Text property  Though that might depend on how often you re calling it  I was testing with a tight loop     This will not scroll if it is called before the textbox is shown  or if the textbox is otherwise not visible  e g  in a different tab of a TabPanel   See TextBox AppendText   not autoscrolling  This may or may not be important  depending on if you require autoscroll when the user can t see the textbox   It seems that the alternative method from the other answers also don t work in this case  One way around it is to perform additional scrolling on the VisibleChanged event   textBox VisibleChanged     sender  e    gt        if  textBox Visible                textBox SelectionStart   textBox TextLength          textBox ScrollToCaret                 Internally  AppendText does something like this   textBox Select textBox TextLength   1  0   textBox SelectedText   textToAppend    But there should be no reason to do it manually    If you decompile it yourself  you ll see that it uses some possibly more efficient internal methods  and has what seems to be a minor special case

User · Answer

This will scroll to the end of the textbox when the text is changed  but still allows the user to scroll up  outbox SelectionStart   outbox Text Length  outbox ScrollToEnd      tested on Visual Studio Enterprise 2017

User · Answer

I needed to add a refresh   textBox1 SelectionStart   textBox1 Text Length  textBox1 ScrollToCaret    textBox1 Refresh

User · Answer

I found a simple difference that hasn t been addressed in this thread   If you re doing all the ScrollToCarat   calls as part of your form s Load   event  it doesn t work   I just added my ScrollToCarat   call to my form s Activated   event  and it works fine   Edit  It s important to only do this scrolling the first time form s Activated event is fired  not on subsequent activations   or it will scroll every time your form is activated  which is something you probably don t want   So if you re only trapping the Activated   event to scroll your text when your program loads  then you can just unsubscribe to the event inside the event handler itself  thusly   Activated -  new System EventHandler this Form1 Activated     If you have other things you need to do each time your form is activated  you can set a bool to true the first time your Activated   event is fired  so you don t scroll on subsequent activations  but can still do the other things you need to do   Also  if your TextBox is on a tab that isn t the SelectedTab  ScrollToCarat   will have no effect   So you need at least make it the selected tab while you re scrolling   You can wrap the code in a YourTab SuspendLayout    and YourTab ResumeLayout false   pair if your form flickers when you do this   End of edit  Hope this helps

User · Answer

With regards to the comment by Pete about a TextBox on a tab  the way I got that to work was adding textBox1 SelectionStart   textBox1 Text Length  textBox1 ScrollToCaret     to the tab s Layout event

User · Answer

For anyone else landing here expecting to see a webforms implementation  you want to use the Page Request Manager s endRequest event handler  https   stackoverflow com a 1388170 1830512   Here s what I did for my TextBox in a Content Page from a Master Page  please ignore the fact that I didn t use a variable for the control   var prm   Sys WebForms PageRequestManager getInstance     function EndRequestHandler         if   get   lt      TextBox StatusWindow FindControl  StatusTxtBox    ClientID   gt       null             get   lt      TextBox StatusWindow FindControl  StatusTxtBox    ClientID   gt    scrollTop             get   lt      TextBox StatusWindow FindControl  StatusTxtBox    ClientID   gt    scrollHeight           prm add endRequest EndRequestHandler

[c#] How do I automatically scroll to the bottom of a multiline text box?

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