textbox的textmode取为multiline多行时，其maxlength不起作用

方法一：验证控件验证(经实践可行)

Setting the Maxength of a TextBox when it is in Multiline, You can use RegularExpressionValidator control as shown below

<asp:TextBox ID="txtConclusion" MaxLength="200" TextMode="MultiLine" Height="100px" Width="400px" runat="server" />
<asp:RegularExpressionValidator ID="txtConclusionValidator1" ControlToValidate="txtConclusion" Text="超过200字" ValidationExpression="^[\s\S]{0,200}$" runat="server" />

方法二：弹出对话框提示
1.html代码

textbox的textmode取为multiline多行时，其maxlength不起作用

<HTML>

<HEAD>

<title>WebForm6</title>
textbox的textmode取为multiline多行时，其maxlength不起作用

2.cs代码

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

方法三：自定义控件

Multiline TextBox with MaxLength Validation

http://www.codeproject.com/KB/aspnet/Textarea_Length_Validator.aspx