Page.IsPostBack Property
Definition
Important
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Gets a value that indicates whether the page is being rendered for the first time or is being loaded in response to a postback.
public:
property bool IsPostBack { bool get(); };[System.ComponentModel.Browsable(false)]
public bool IsPostBack { get; }[<System.ComponentModel.Browsable(false)>]
member this.IsPostBack : boolPublic ReadOnly Property IsPostBack As BooleanProperty Value
true if the page is being loaded in response to a client postback; otherwise, false.
- Attributes
Examples
The following example shows how to test the value of the IsPostBack property when the page is loaded in order to determine whether the page is being rendered for the first time or is responding to a postback. If the page is being rendered for the first time, the code calls the Page.Validate method.
The page markup (not shown) contains RequiredFieldValidator controls that display asterisks if no entry is made for a required input field. Calling Page.Validate causes the asterisks to be displayed immediately when the page is rendered, instead of waiting until the user clicks the Submit button. After a postback, you do not have to call Page.Validate, because that method is called as part of the Page life cycle.
private void Page_Load()
{
if (!IsPostBack)
{
// Validate initially to force asterisks
// to appear before the first roundtrip.
Validate();
}
}
Sub Page_Load
If Not IsPostBack
' Validate initially to force the asterisks
' to appear before the first roundtrip.
Validate()
End If
End Sub
Remarks
For an explanation of the difference between postbacks and callbacks, see Implementing Client Callbacks Without Postbacks.
