多行文本框限制输入字符长度(两种方法)

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方法一：弹出对话框提示
1.html代码

<HTML>

<HEAD>

<title>WebForm6</title>

function isOver(sText,len)

{

var intlen=sText.value.length;

if (intlen>len)

{

alert("The content length must Less than or Equal "+len);

sText.focus();

sText.select();

}

</script>

</HEAD>

<asp:TextBox id="txtName" style="Z-INDEX: 102; LEFT: 200px; POSITION: absolute; TOP: 104px" runat="server"

TextMode="MultiLine" Height="112px" Width="271px"></asp:TextBox>

</form>

</body>

</HTML>

2.cs代码

private void Page_Load(object sender, System.EventArgs e)

{

this.txtName.Attributes.Add("onblur","isOver(this,1000);");

}

方法二：限制用户继续输入

<HEAD>

<!-- TWO STEPS TO INSTALL LIMIT TEXTAREA:

1. Copy the coding into the HEAD of your HTML document

2. Add the last code into the BODY of your HTML document -->

<!-- Begin

function textCounter(field, countfield, maxlimit) {

if (field.value.length > maxlimit) // if too long

trim it!

field.value = field.value.substring(0, maxlimit);

// otherwise, update 'characters left' counter

else

countfield.value = maxlimit - field.value.length;

}

// End -->

</SCRIPT>

</HEAD>

<BODY>

<font size="1" face="arial, helvetica, sans-serif">( You may enter up to 125

characters. )<br>

<textarea name="message" wrap="physical" cols="28" rows="4" onKeyDown="textCounter(this.form.message,this.form.remLen,125);"

onKeyUp="textCounter(this.form.message,this.form.remLen,125);"></textarea>

<br>

<input readonly type="text" name="remLen" size="3" maxlength="3" value="125"> characters

left</font>

</form>

</center>

<font face="arial, helvetica" SIZE="-2">Free JavaScripts provided<br>

by <a href="http://javascriptsource.com">The JavaScript Source</a></font>

</center>

</BODY>