How to limit the number of characters allowed in a textbox?

Question

<asp:TextBox ID="txtBodySMS" runat="server" Rows="10"                          
           TextMode="MultiLine" Width="100%"></asp:TextBox>

This is my text box. How do I limit the number of characters a user can type inside it?

clamchoda · Answer 1 · 2019-03-20T19:16:33.400

MaxLength does not apply to ASP.NET to Textboxes with TextMode="MultiLine". An easy way to do this and keep your MultiLine mark up would be to add:

onkeypress="return this.value.length<=10"

with 10 being the limit. Like so:

<asp:TextBox ID="txtBodySMS" runat="server" Rows="10" onkeypress="return this.value.length<=10" TextMode="MultiLine" Width="100%"></asp:TextBox>

EDIT Option One (Server side) The above example has some issues pointed out over the years. The underlying problem is a multi-line textBox is rendered as a text-area and MaxLength is removed. We can also fix in the C# or VB asp.net code behind of the page by forcing the re-attachment of MaxLength instead of attaching onkeypress.

    protected void Page_Load(object sender, EventArgs e)
    {
        txtBodySMS.Attributes.Add("maxlength", "10");
    }

EDIT Option Two (Client side): Here's a simple jquery solution. Include the following script in your head instead of attaching onkeypress or editing the server side code.

    $(document).ready(function () {
        $(".MultiLineLimit").on('change keydown paste input', function () {
            this.value = (this.value.length <= 10 ? this.value : this.value.substring(0, 10));
        });
    });

Now just add the MultiLineLimitclass to any of your <asp:TextBox> textbox of TextMode="MultiLine".

<asp:TextBox ID="txtBodySMS" CssClass="MultiLineLimit" runat="server" Rows="10" TextMode="MultiLine" Width="100%"></asp:TextBox>

Remember in either scenario client side validation can be removed. If your storing this in a database it should always be validated server side as well.

But then when you reach the character limit - the textbox is frozen, you cant delete anything from it — DNKROZ, Mar 16 '14 at 21:54
this works on keydowns, but using ctrl+v to paste a large amount of text into the box breaks this, and you can still enter as much as you like — Rich, Oct 08 '14 at 10:43
@Rich You were both right I did not notice that over the years. I have fixed — clamchoda, Mar 20 '19 at 18:25

score 19 · Accepted Answer · edited Apr 13 '18 at 15:50

19

This did it for me. I did not keep the MultiLine property.

<asp:TextBox ID="txtBodySMS" runat="server" Rows="10" MaxLength="2" Width="100%"></asp:TextBox>

edited Apr 13 '18 at 15:50

TylerH

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answered May 24 '11 at 14:12

Beginner

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live-love · Answer 3 · 2014-11-07T15:55:55.233

Maximum character length Validation (Maximum 8 characters allowed)

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "TextBox1" ID="RegularExpressionValidator1" ValidationExpression = "^[\s\S]{0,8}$" runat="server" ErrorMessage="Maximum 8 characters allowed."></asp:RegularExpressionValidator>

Minimum character length Validation (Minimum 8 characters required)

<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "TextBox2" ID="RegularExpressionValidator2" ValidationExpression = "^[\s\S]{8,}$" runat="server" ErrorMessage="Minimum 8 characters required."></asp:RegularExpressionValidator>

Minimum and Maximum character length Validation (Minimum 5 and Maximum 8 characters required)

<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "TextBox3" ID="RegularExpressionValidator3" ValidationExpression = "^[\s\S]{5,8}$" runat="server" ErrorMessage="Minimum 5 and Maximum 8 characters required."></asp:RegularExpressionValidator>

score 12 · Answer 4 · answered May 24 '11 at 14:01

12

MaxLength="Int32"

<asp:TextBox ID="txtBodySMS" runat="server" Rows="10" MaxLength="220"                         
           TextMode="MultiLine" Width="100%"></asp:TextBox>

answered May 24 '11 at 14:01

Senad Meškin

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that does not work, they are still able to enter more than 220 characters – Beginner May 24 '11 at 14:06
then something is wrong, this is microsoft documented property – Senad Meškin May 24 '11 at 14:10
7

is not, need to take out multiline – Beginner May 24 '11 at 14:12

score 4 · Answer 5 · answered May 24 '11 at 14:12

4

AFAIK maxlength has never worked in conjunction with the "multiline" mode. Therefore I would suggest some client-side js/jquery and server-side to get around the problem.

answered May 24 '11 at 14:12

Mike

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Alok singh · Answer 6 · 2016-03-09T09:12:17.943

2

Just type below two line in .cs page load

textbox1.Attributes.Remove("MaxLength");
textbox1.Attributes.Add("MaxLength", "30");

Hope it will help !

edited Mar 09 '16 at 09:12

answered Mar 09 '16 at 08:55

Alok singh

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3

Top voted answer does not work when user is copy/pasting into textbox. So a modified version of this answer (i.e. handling in javascript/jquery) works best. – Douglas Timms Mar 08 '19 at 21:25

score 1 · Answer 7 · edited Oct 08 '20 at 22:54

1

<asp:TextBox ID="txtBodySMS" runat="server" Rows="10" MaxLength="220" 
    TextMode="MultiLine" Width="100%">
</asp:TextBox>

edited Oct 08 '20 at 22:54

derloopkat

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answered Oct 08 '20 at 22:22

Zimi

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Code-only answers are low quality answers. – Taslim Oseni Oct 08 '20 at 23:06
you need to add a description to your code or it will be considered as low-quality answer – MuhanadY Oct 09 '20 at 05:30

score 0 · Answer 8 · answered Dec 08 '15 at 03:35

It is important to note that using MaxLength alone (with no other properties to add, just like the other answers) works ONLY for projects in .NET Framework 4.5 and above.

I'm using 4.5, and it worked for my project

<asp:TextBox ID="txtSample" MaxLength="3" runat="server"/>

TextBox.MaxLength Property (MSDN Documentation)

score 0 · Answer 9 · answered May 24 '11 at 14:02

0

Set the MaxLength attribute to the number of characters.

answered May 24 '11 at 14:02

Tom Robinson

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score 0 · Answer 10 · edited May 24 '11 at 14:34

0

You are looking for MaxLength: Look here

edited May 24 '11 at 14:34

Awais Qarni

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answered May 24 '11 at 14:02

Theofanis Pantelides

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score 0 · Answer 11 · edited May 24 '11 at 14:46

0

Have you tried setting the MaxLength Property on the TextBox? for Reference

edited May 24 '11 at 14:46

Awais Qarni

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answered May 24 '11 at 14:02

Peter Mourfield

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score 0 · Answer 12 · answered May 19 '20 at 18:43

It seems to be a curious oversight in the design of ASP.NET (leaving aside the anomaly with textareas) that you can set the MaxLength property of a textbox but there seems to be no way provided to enforce this limit server-side without explicitly adding a validator. That's a nuisance if you have lots of fields and just want to be sure that no-one is subventing the limits of the form by injecting their own POST data. So I wrote this, which seems to do the trick - obviously you might not want to force Response.End

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load

        Dim colControls As Collection = New Collection
        getControlList(colControls, Me)
        For Each ctlNextPlease As Control In colControls
            If TypeOf (ctlNextPlease) Is TextBox Then
                Dim ctlTextBox As TextBox = ctlNextPlease
                If Len(Request(ctlTextBox.ID)) > ctlTextBox.MaxLength Then
                    Response.Write("The value <i>" & Request(ctlTextBox.ID) & "</i> submitted for <b>" & ctlTextBox.ID & "</b> exceeds the permitted maximum length (" & ctlTextBox.MaxLength & ") for that value")
                    Response.End()
                End If
            End If
        Next
...
End Sub

Public Shared Sub getControlList(ByRef colControls As Collection, ByVal rootControl As Control)
  colControls.Add(rootControl)
  If rootControl.Controls.Count > 0 Then
    For Each controlToSearch As Control In rootControl.Controls
      getControlList(colControls, controlToSearch)
    Next
  End If
End Sub

score 0 · Answer 13 · edited Oct 27 '12 at 21:08

0

Add an extender of type FliterTextBoxExtender for your text box
it should appear like that

<asp:TextBox ID="TxtCellular" runat="server"></asp:TextBox>
<asp:FilteredTextBoxExtender ID="TxtCellular_FilteredTextBoxExtender" 
                    runat="server" Enabled="True" TargetControlID="TxtCellular" FilterType="Numbers">
</asp:FilteredTextBoxExtender>

edited Oct 27 '12 at 21:08

Mario S

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answered Feb 07 '12 at 18:15

Solvator

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How to limit the number of characters allowed in a textbox?

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