Implementing MaxLength for asp textbox

  • Thread starter Thread starter Not Me
  • Start date Start date
N

Not Me

Hi there,

There are hundreds of messages with different solutions on how to limit
the number of characters for a text box in ASP.net, none of which I can
get to work!!

I do lie, because using asp validators I can get a quick solution, but
I'd rather prevent the user from entering the characters in the first
place, rather than just telling them they've entered too much.

Many solutions tell me to use onkeydown etc. in the textbox parameters
- when I do this I get errors saying it's not allowed.. I seem to be
able to use attributes.add but nothing happens then. Also I'm being
told I need a 'type' parameter in my script, wheras all of the examples
just use 'language'..

here's my example code anyway, which is 'attached' to the textbox by
attributes.add.

<script type="text/jscript" language="jscript">
function LimitMultiLineLength(obj)
{
var iKey;
var eAny_Event = window.event;
iKey = eAny_Event.keyCode;
var re
re = new RegExp("\r\n","g")
x = obj.value.replace(re,"").length ;
if ((x >= obj.maxLength) && ((iKey > 33 && iKey <
255) || (iKey > 95 && iKey < 106)) && (iKey != 13))
{
if (obj.ErrorMessage )
{
alert(obj.ErrorMessage);
}
window.event.returnValue=false;
}
}
</script>

whereas nothing happens in IE, firefox is kind enough to tell me that
'LimitMultiLineLength is not defined' - so I'm guessing at least it's
being looked for.

any ideas? I thought there'd be a really simple solution to this!
(maybe there is...)

Cheers,
Chris
 
any ideas? I thought there'd be a really simple solution to this!
(maybe there is...)
Click to expand...

Er, well unless I'm missing something here...

<asp:TextBox ID="MyTextBox" runat="server" MaxLength="100" />
 
Mark said:
Er, well unless I'm missing something here...

<asp:TextBox ID="MyTextBox" runat="server" MaxLength="100" />
Click to expand...

D'oh, also forgot to mention, it's a multiline text box :p

cheers,
Chris
 
Not said:
Hi there,

There are hundreds of messages with different solutions on how to limit
the number of characters for a text box in ASP.net, none of which I can
get to work!!

I do lie, because using asp validators I can get a quick solution, but
I'd rather prevent the user from entering the characters in the first
place, rather than just telling them they've entered too much.

Many solutions tell me to use onkeydown etc. in the textbox parameters
- when I do this I get errors saying it's not allowed.. I seem to be
able to use attributes.add but nothing happens then. Also I'm being
told I need a 'type' parameter in my script, wheras all of the examples
just use 'language'..
Click to expand...

The "language" attribute on the "script" tag has been deprecated. The
type attribute replaces it. And unfortunately, most examples of
JavaScript on the web (I guess around 90% of them or more) are showing a
lot of bad practices. It's really terrible.

A good reference to learn JavaScript is David Flanagan's book
"JavaScript, the definitive guide", which was recently released in its
5th edition.

This should work on IE and Mozilla-based browsers:

<script type="text/javascript">
var MAX_LENGTH = 10;

function showLength( evt )
{
if ( window.event )
{
evt = window.event;
}

var taTest = null;

if ( evt.srcElement )
{
taTest = evt.srcElement;
}
if ( evt.target )
{
taTest = evt.target;
}
if ( !taTest )
{
throw "Unknown target";
}

var iLength = taTest.value.length;

if ( iLength > MAX_LENGTH )
{
taTest.value = taTest.value.substring( 0, MAX_LENGTH );
iLength = MAX_LENGTH;
}

var nSpanStatus = document.getElementById( "spanStatus" );
nSpanStatus.firstChild.nodeValue = iLength;

if ( iLength >= MAX_LENGTH )
{
nSpanStatus.style.color = "Red";
}
else
{
nSpanStatus.style.color = "Black";
}
}

function attachEvent()
{
var nTaTest = document.getElementById( "taTest" );
nTaTest.onkeyup = showLength;
}

</script>

with

<body onload="attachEvent();">

and

<form id="frmMain" action="HTMLPage1.htm">

<textarea id="taTest" rows="10" cols="20"
onkeyup="showLength();"></textarea>
<br /><br />
<span id="spanStatus" style=color: Black;">&nbsp;</span>

</form>

HTH,
Laurent
 
This should work on IE and Mozilla-based browsers:

<script type="text/javascript">
var MAX_LENGTH = 10;

function showLength( evt )
{
if ( window.event )
{
evt = window.event;
}

var taTest = null;

if ( evt.srcElement )
{
taTest = evt.srcElement;
}
if ( evt.target )
{
taTest = evt.target;
}
if ( !taTest )
{
throw "Unknown target";
}

var iLength = taTest.value.length;

if ( iLength > MAX_LENGTH )
{
taTest.value = taTest.value.substring( 0, MAX_LENGTH );
iLength = MAX_LENGTH;
}

var nSpanStatus = document.getElementById( "spanStatus" );
nSpanStatus.firstChild.nodeValue = iLength;

if ( iLength >= MAX_LENGTH )
{
nSpanStatus.style.color = "Red";
}
else
{
nSpanStatus.style.color = "Black";
}
}

function attachEvent()
{
var nTaTest = document.getElementById( "taTest" );
nTaTest.onkeyup = showLength;
}

</script>

with

<body onload="attachEvent();">

and

<form id="frmMain" action="HTMLPage1.htm">

<textarea id="taTest" rows="10" cols="20"
onkeyup="showLength();"></textarea>
<br /><br />
<span id="spanStatus" style=color: Black;">&nbsp;</span>

</form>

HTH,
Laurent
Click to expand...

Thank you very much Laurent, works perfectly!! :)

cheers,
Chris
 
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