Impersonation is independent of the authentication mode configured using the authentication configuration element. The authentication element is used to determine, the User property of the current HttpContext. Impersonation is used to determine the WindowsIdentity of the ASP.
By default, ASP. Configured to use Windows Authentication mode, which applies the Windows identity supplied by I is to the User's property of the current HttpContext object. This enables determine the identity supplied by IIS through the user property (the user Name was blank when Anonymou s identification is used), but does does use the supplied identity as the WindowsIdentity for the current page. The WindowsIdentity for an application are used when determining if the application have access to a particular file or NETW Ork resource.
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ASP. NET Security