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Text box to accept only number

, 23 Apr 2011 CPOL
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Text box to accept only number
   <SCRIPT language="Javascript">
      function isNumberKey(evt)
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode > 31 && (charCode < 48 || charCode > 57))
            return false;
         return true;
      <INPUT id="txtChar" onkeypress="return isNumberKey(event)" type="text" name="txtChar">
Just paste the Script Section in the Head section and in on key press call the function.
For C#, just paste the following code:
function allownumbers(e) {
        var key = window.event ? e.keyCode : e.which;
        var keychar = String.fromCharCode(key);
        var reg = new RegExp("[0-9.]")
        if (key == 8) {
            keychar = String.fromCharCode(key);

And in PageLoad:
txtNum.Attributes.Add("onkeypress", "javascript:return allownumbers(event);");


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


About the Author

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I am Prasanta Banerjee. I am an Asp.Net Developer. My site:
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Comments and Discussions

QuestionGood Solution PinmemberAlireza_136220-Mar-13 23:24 
GeneralMy vote of 2 Pinmemberniubay11-Sep-12 4:31 
GeneralRe: by small digits I mean something like: 1.2345, 6.78 etc I ... PinmemberUnruled Boy24-Apr-11 13:14 
GeneralRe: Agreed. Something like this regular expression /^-?[0-9]+(\.... Pinmemberdanlobo30-Dec-11 0:32 
GeneralRe: Negative values you just have to program to allow the minus ... PinmemberEdMan19624-Apr-11 4:08 
GeneralRe: The keyboard remapping just assigns different characters to ... PinprotectorAspDotNetDev24-Apr-11 1:44 
GeneralRe: For starters you can remap your keyboard but also, the world... PinmemberEdMan19623-Apr-11 23:57 
GeneralReason for my vote of 5 exclent Pinmemberlovepreet_shota18-Jun-11 18:15 
GeneralThis is all well and good unless of course my keyboards numb... PinmemberEdMan19623-Apr-11 3:40 
This is all well and good unless of course my keyboards number keys don't match char codes 31 and 48 to 57.... You ought to be using '9' instead of 57 etc. to allow for different keyboards. Otherwise, this is a good example (though vars in C# are messy if you ask me. Why not use some proper types? :/ )
GeneralRe: What do you mean? How would your keyboard number keys use di... PinprotectorAspDotNetDev23-Apr-11 19:51 
GeneralRe: what if small digits or negative values? I think using regex... PinmemberUnruled Boy24-Apr-11 4:05 
GeneralExplanation needed PinsubeditorIndivara18-Apr-11 13:05 
GeneralRe: Explanation needed Pinmemberpashad27-Dec-11 19:52 

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