TextBox.AutoPostBack Property
Gets or sets a value that indicates whether an automatic postback to the server occurs when the TextBox control loses focus.
Namespace: System.Web.UI.WebControls
Assembly: System.Web (in System.Web.dll)
Use the AutoPostBack property to specify whether an automatic postback to the server will occur when the TextBox control loses focus. Pressing the ENTER or the TAB key while in the TextBox control is the most common way to change focus.
 Note |
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If the TextBox control's parent container contains a button marked as the default button (for example, if the container's DefaultButton or DefaultButton property is set), the default button's Click event is not raised in response to the automatic postback. |
This property cannot be set by themes or style sheet themes. For more information, see ThemeableAttribute and ASP.NET Themes and Skins.
| Topic | Location |
|---|---|
| How to: Respond to Changes in a TextBox Web Server Control | Building ASP .NET Web Applications |
| How to: Specify Whether ASP.NET Web Server Controls Post to the Server | Building ASP .NET Web Applications |
| How to: Respond to Changes in a TextBox Web Server Control | Building ASP .NET Web Applications |
| How to: Specify Whether ASP.NET Web Server Controls Post to the Server | Building ASP .NET Web Applications |
The following example shows how to use the AutoPostBack property to automatically display the sum of the values entered in the text boxes when the TextBox control loses focus.
| Security Note |
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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 Page_Load(Object sender, EventArgs e) { int Answer; // Due to a timing issue with when page validation occurs, call the // Validate method to ensure that the values on the page are valid. Page.Validate(); // Add the values in the text boxes if the page is valid. if(Page.IsValid) { 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 /> The two values are automatically added <br /> when you tab out of the text boxes. <br /> </td> </tr> <tr> <td colspan="5"> </td> </tr> <tr align="center"> <td> <asp:TextBox ID="Value1" Columns="2" MaxLength="3" AutoPostBack="True" Text="1" runat="server"/> </td> <td> + </td> <td> <asp:TextBox ID="Value2" Columns="2" MaxLength="3" AutoPostBack="True" 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 />" EnableClientScript="False" 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 />" EnableClientScript="False" Display="Dynamic" runat="server"/> </td> <td colspan="2"> <asp:RequiredFieldValidator ID="Value2RequiredValidator" ControlToValidate="Value2" ErrorMessage="Please enter a value.<br />" EnableClientScript="False" 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 />" EnableClientScript="False" Display="Dynamic" runat="server"/> </td> <td>   </td> </tr> </table> </form> </body> </html>
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.
