Specifying maxlength for multiline textbox

Question

I'm trying to use asp:

<asp:TextBox ID="txtInput" runat="server" TextMode="MultiLine"></asp:TextBox>

and i want a way to specify the maxlength property ,but apparently there is not such for multiline textbox. I've been trying to use some javascript for the onkeypress event onkeypress="return textboxMultilineMaxNumber(this,maxlength)"

function textboxMultilineMaxNumber(txt, maxLen) {
            try {
                if (txt.value.length > (maxLen - 1)) return false;

            } catch (e) {
            }
            return true;
        }

while working fine the problem with this javascript function is that after writing characters it doesn't allow you to delete and substitute any of them, such a behavior is not desired.

Have you got any idea what can i possibly change in the above code to avoid that or any other ways to get round it. Thank you!!

Answer 1

Hi, try this javascript:

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

On the control invoke it like this:

<asp:TextBox Rows="5" Columns="80" ID="txtCommentsForSearch" MaxLength='1999' onkeyDown="checkTextAreaMaxLength(this,event,'1999');"  TextMode="multiLine" runat="server"> </asp:TextBox>

You could also just use the checkSpecialKeys function to validate the input on your javascript implementation.

Answer 2

Have a look at this. The only way to solve it is by javascript as you tried.

EDIT: Try changing the event to keypressup.

Answer 3

you might be trying to run the function in firefox run it in IE it will work..