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Determine how an ASP.NET Web page was invoked

Determine how an ASP.NET Web page was invoked

Examine the values of the following Page class properties, and then refer the table to determine how the page was invoked:

  • IsPostBack

  • PreviousPage

  • IsCrossPagePostBack

  • IsCallback

The following table lists ways in which a page can be invoked and the corresponding Page property values.

Invocation method

Property values

Original request

  • IsPostBack is set to false.

  • PreviousPage is set to null (Nothing in Visual Basic).

  • IsCallback is set to false.

Postback

  • IsPostBack is set to true.

  • PreviousPage is set to null (Nothing in Visual Basic).

  • IsCallback is set to false.

Cross-page posting

  • IsPostBack is set to false.

  • PreviousPage references the source page.

  • IsCrossPagePostBack is set to true.

  • IsCallback is set to false.

Server transfer

  • IsPostBack is set to false.

  • PreviousPage references the source page.

  • IsCrossPagePostBack that is referenced in the PreviousPage is set to false.

  • IsCallback is set to false.

Callback

  • IsPostBack is set to false.

  • PreviousPage is set to null (Nothing in Visual Basic).

  • IsCallback is set to true.

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2 replies »

  1. It is often useful to know how an ASP.NET Website was invoked: whether by an unique ask for (an HTTP GET), a postback (an HTTP POST), a cross-page publish from another web page (an HTTP POST), or a exchange from another web page using the Transfer technique or using a callback from the web browser.

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