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TextBox.MaxLength Property

Gets or sets the maximum number of characters allowed in the text box.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

[ThemeableAttribute(false)]
public virtual int MaxLength { get; set; }
<asp:TextBox MaxLength="Int32" />

Property Value

Type: System.Int32
The maximum number of characters allowed in the text box. The default is 0, which indicates that the property is not set.

ExceptionCondition
ArgumentOutOfRangeException

The specified width is less than 0.

Use the MaxLength property to limit the number of characters that can be entered in the TextBox control.

NoteNote:

This property is applicable only when the TextMode property is set to TextBoxMode.SingleLine or TextBoxMode.Password.

This property cannot be set by themes or style sheet themes. For more information, see ThemeableAttribute and ASP.NET Themes and Skins Overview.

TopicLocation
How to: Set ASP.NET Web Server Control PropertiesBuilding ASP .NET Web Applications
How to: Set ASP.NET Web Server Control PropertiesBuilding ASP .NET Web Applications

The following code example demonstrates how to use the MaxLength property to limit the number of characters allowed in the TextBox control to 3.

Security noteSecurity Note:

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" > 

<head>
    <title> TextBox Example </title>
<script runat="server">

      protected void AddButton_Click(Object sender, EventArgs e)
      {
         int Answer;

         Answer = Convert.ToInt32(Value1.Text) + Convert.ToInt32(Value2.Text);

         AnswerMessage.Text = Answer.ToString();

      }

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3> TextBox Example </h3>

      <table>

         <tr>

            <td colspan="5">

               Enter integer values into the text boxes. <br />
               Click the Add button to add the two values. <br />
               Click the Reset button to reset the text boxes.

            </td>

         </tr>

         <tr>

            <td colspan="5">

               &nbsp;

            </td>

         </tr>

         <tr align="center">

            <td>

               <asp:TextBox ID="Value1"
                    Columns="2"
                    MaxLength="3"
                    Text="1"
                    runat="server"/>

            </td>

            <td>

               + 

            </td>

            <td>

               <asp:TextBox ID="Value2"
                    Columns="2"
                    MaxLength="3"
                    Text="1"
                    runat="server"/>

            </td>

            <td>

               =

            </td>

            <td>

               <asp:Label ID="AnswerMessage"
                    runat="server"/>

            </td>

         </tr>

         <tr>

            <td colspan="2">

               <asp:RequiredFieldValidator
                    ID="Value1RequiredValidator"
                    ControlToValidate="Value1"
                    ErrorMessage="Please enter a value.<br />"
                    Display="Dynamic"
                    runat="server"/>

               <asp:RangeValidator
                    ID="Value1RangeValidator"
                    ControlToValidate="Value1"
                    Type="Integer"
                    MinimumValue="1"
                    MaximumValue="100"
                    ErrorMessage="Please enter an integer <br /> between than 1 and 100.<br />"
                    Display="Dynamic"
                    runat="server"/>

            </td>

            <td colspan="2">

               <asp:RequiredFieldValidator
                    ID="Value2RequiredValidator"
                    ControlToValidate="Value2"
                    ErrorMessage="Please enter a value.<br />"
                    Display="Dynamic"
                    runat="server"/>

               <asp:RangeValidator
                    ID="Value2RangeValidator"
                    ControlToValidate="Value2"
                    Type="Integer"
                    MinimumValue="1"
                    MaximumValue="100"
                    ErrorMessage="Please enter an integer <br /> between than 1 and 100.<br />"
                    Display="Dynamic"
                    runat="server"/>

            </td>

            <td>

               &nbsp

            </td>

         </tr>

         <tr align="center">

            <td colspan="4">

               <asp:Button ID="AddButton"
                    Text="Add"
                    OnClick="AddButton_Click"
                    runat="server"/>

            </td>

            <td>

               &nbsp;

            </td>

         </tr>

      </table>

   </form>

</body>
</html>

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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