Name

IsPostBack

Synopsis

Boolean = Page.IsPostBack

Returns a Boolean value that indicates if the page is loaded for the first time (False) or is loaded as a result of the client postback (True). This property comes handy for the logic that needs to be executed the first time the page is executed or every time the page is posted back to itself, depending on how you structure your If statement.

Parameters

Boolean

A Boolean value that indicates if the page is loaded for the first time or is loaded as a result of the client postback.

Example

The code example below uses the IsPostBack property to display different messages in the Label control, depending on whether the page is loaded for the first time or is loaded as a result of the client postback. The first time the page is loaded, the IsPostBack property returns False, causing the string “Non-PostBack” to be displayed. Clicking the button posts the page back to itself, causing IsPostBack to return True and the string “PostBack” to be displayed. 

<%@ Page Language="vb" %>
<html>
   <head>
      <title></title>
      <script runat="server">
         Sub Page_Load(  )
            If Page.IsPostBack Then
               Message.Text = "PostBack"
            Else
               Message.Text = "Non-PostBack"
            End If
         End Sub
      </script>
   </head>
<body>
   <form runat="server">
      <asp:button id="post" Text="Post page" runat="server"/>
      <asp:label id="Message" runat="server"/>
   </form>
</body>
</html>

Notes

The IsPostBack property will return True only for pages that contain a <form> element with the runat="server" attribute and at least ...

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