Click here to Skip to main content
Click here to Skip to main content

Check maxlength of multiline textbox in javascript

, 21 Feb 2012
Rate this:
Please Sign up or sign in to vote.
This post will help you to resolve problem of checking maxlength of Multilie textbox (IE & Firefox)

Introduction

ASP.net provides textbox controls for data inputs and they are used vastly on the websites. TextMode='Multiline' property of textbox is used everywhere to input comments or any large data.

With my program assignment I came across a problem to set MaxLength for multiline textbox, i.e after some specified length, the textbox should not accept any characters.

(Note: This solution will only tested & recommended for IE (5+) & Firefox )

Details

The MaxLength property of textbox control works fine if Multiline mode is not set, but if TextMode='Multiline' is set in aspx page then this property is of no use and user can input any number of characters inspite of setting maxlength.

Finally I was able to find a solution and wanted to share it with you all.

This example requires just very basic knowledge of java script so don’t be scared I promise this will be one of the easiest java scripts that can solve a complex problem.

Add the following to your Multiline box in aspx page:

<asp:TextBox Rows="5" Columns="80" ID="txtCommentsForSearch" MaxLength="10" onkeyDown="return checkTextAreaMaxLength(this,event,'10');"  TextMode="multiLine" CssClass="textArea" runat="server"> </asp:TextBox>
        

*txtCommentsForSearch-This is asp.net control that is having multiline property set

I have used MaxLength='1999', same property you have to use in underlying javascript file also. I have also passed this length to the calling javascript method, so that in case the MaxLength is not accessible then can be picked from parameters of javascript method.

Add the following to your javascript file:

// JScript File

function checkTextAreaMaxLength(textBox, e, length) {

    var mLen = textBox["MaxLength"];
    if (null == mLen)
        mLen = length;

    var maxLength = parseInt(mLen);
    if (!checkSpecialKeys(e)) {
        if (textBox.value.length > maxLength - 1) {
            if (window.event)//IE
            {
                e.returnValue = false;
                return false;
            }
            else//Firefox
                e.preventDefault();
        }
    }
}

function checkSpecialKeys(e) {
    if (e.keyCode != 8 && e.keyCode != 46 && e.keyCode != 35 && e.keyCode != 36 && e.keyCode != 37 && e.keyCode != 38 && e.keyCode != 39 && e.keyCode != 40)
        return false;
    else
        return true;
}     

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Surjit Singh Dadhwal
Software Developer (Senior)
India India
Programming is my passion and C# is my friend, Javascript is my first crush..
Surprized!!!, don't be....
I love doing programming and writing efficient code, with the help of code project; I am able to share my experiences too with you all.
 
Thanks for visiting and voting this post.. [Smile | :) ]

Comments and Discussions

 
GeneralDoes not work if user directly pastes the text from clip board Pinmemberarpitk15-Jan-09 0:04 
GeneralRe: Does not work if user directly pastes the text from clip board PinmemberPaul Lockett23-Aug-10 1:16 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web04 | 2.8.140721.1 | Last Updated 22 Feb 2012
Article Copyright 2008 by Surjit Singh Dadhwal
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid