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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.

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

A Visual Studio Web site project with source code is available to accompany this topic: Download.

The following code example demonstrates how to use the TextBox control to get user input. When the user clicks the Add button, the sum of the values entered in the text boxes is displayed.

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>
<html> 

<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>
    <p>
        <asp:TextBox ID="Value1" Columns="2" MaxLength="3" Text="1" runat="server"/>
        +
        <asp:TextBox ID="Value2" Columns="2" MaxLength="3" Text="1" runat="server"/>
        =
        <asp:Label ID="AnswerMessage" runat="server"/>
    </p>
    <p>
        <asp:Button ID="AddButton" Text="Add" OnClick="AddButton_Click" runat="server"/>
    </p>
    <p>
        <asp:RequiredFieldValidator ID="Value1RequiredValidator" ControlToValidate="Value1"
             ErrorMessage="Please enter a value.<br />" Display="Dynamic"
             runat="server"/>
        <asp:RequiredFieldValidator ID="Value2RequiredValidator" ControlToValidate="Value2"
             ErrorMessage="Please enter a value.<br />" Display="Dynamic"
             runat="server"/>
        <asp:RangeValidator ID="Value1RangeValidator" ControlToValidate="Value1"
             Type="Integer" MinimumValue="1" MaximumValue="100" Display="Dynamic"
             ErrorMessage="Please enter an integer <br /> between than 1 and 100.<br />"
             runat="server"/>
        <asp:RangeValidator ID="Value2RangeValidator" ControlToValidate="Value2"
             Type="Integer" MinimumValue="1" MaximumValue="100" Display="Dynamic"
             ErrorMessage="Please enter an integer <br /> between than 1 and 100.<br />"    
             runat="server"/>
    </p>
  </form>
</body>
</html>

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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