Enabling Session Support on the Server
By default, ASP.NET session support for each Web method is turned off. You must explicitly enable session support for each Web method that wants to use session state. This is done by adding the EnableSession property to the WebMethod attribute of your function. The code for a Web method with the EnableSession property set to true, and which accesses the HttpSessionState object, is shown below.
Public Function IncrementSessionCounterX() As Integer
Dim counter As Integer
If Context.Session("Counter") Is Nothing Then
counter = 1
counter = Context.Session("Counter") + 1
Context.Session("Counter") = counter
As you might expect, if you enable session support for one Web method, that does not imply that it is enabled for another Web method. In fact, the Context.Session property will be null if EnableSession is not explicitly set to True for a particular Web method.
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