JS判断

 <!--限制输入的字符长度-->
    <script language="javascript" type="text/javascript">

        function MaxLength(field, maxlimit) {
            var j = field.value.replace(/[^\x00-\xff]/g, "**").length;
            //alert(j); 
            var tempString = field.value;
            var tt = "";
            if (j > maxlimit) {
                for (var i = 0; i < maxlimit; i++) {
                    if (tt.replace(/[^\x00-\xff]/g, "**").length < maxlimit)
                        tt = tempString.substr(0, i + 1);
                    else
                        break;
                }
                if (tt.replace(/[^\x00-\xff]/g, "**").length > maxlimit)
                    tt = tt.substr(0, tt.length - 1);
                field.value = tt;
            }
            else {
                ;
            }
        } 
    </script>

   调用:    <asp:TextBox ID="txtother" runat="server" TextMode="MultiLine" Rows="2" Width="100%"
                        CssClass="Texr"  onpropertychange="MaxLength(this,200);"></asp:TextBox>

 限制多行文本框字符限制：

  <asp:TextBox ID="txtinsertTitleDescription" runat="server" TextMode="MultiLine" Rows="2"
                        Width="99%" onkeyup="this.value=this.value.substr(0,200)" onpaste="return false"> </asp:TextBox>

    <!--页面回车加载数据-->
    <script type="text/javascript">
        $(function () {
            $("#<%= TxtNameCh.ClientID %>").keydown(function (e) {
                if (e.keyCode == 13) {
                     var btnmessage = document.getElementById("<%=btnmessage.ClientID %>").click();

                     return false;
                }
            });
        });
    </script>

 

  <!--限制输入2个小数点-->
    <script type="text/javascript">
        function fn(text) {
            var k = "";
            var k = text.value;
            text.value = text.value.replace(/[^\d\.]/g, '');
            if (k.indexOf('.') > -1) {
                var s = k.substring(text.value.indexOf('.') + 1)
                if (s.length > 2) {
                    text.value = k.substring(0, k.length - 1);
                }
            }
        }
    </script>

调用:   <asp:TextBox ID="txtweight" runat="server" Width="100px" onKeyUp="fn(this);" 
                                        CssClass="Texr" MaxLength="7"></asp:TextBox>