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When I am trying to access(view) a sharepoint image from asp.net application I am getting 401 Unauthorised error.

I am using following code: Dim webReq As WebRequest Dim webRes As WebResponse

    webReq = WebRequest.Create("imageUrl")
    webReq.UseDefaultCredentials = True
    webReq.PreAuthenticate = True
    webReq.Credentials = CredentialCache.DefaultCredentials

P.S I: I am able to view the image in the .net application from development server. Issue is when i hosted application to QA server. QA server is the Sharepoint server where image resides.

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Apparently, when we are connecting from asp.net application to any other web application (in my case sharepoint) , by using above code the windows credentials are not passed.In order to pass the user windows credentials to the other web application , we need to use impersonation in code. In my case impersonation is disabled in IIS, but via code I temporarily enabled it.

 Dim winID As WindowsIdentity = 
 CType(HttpContext.Current.User.Identity,WindowsIdentity)

    Dim ctx As WindowsImpersonationContext = Nothing

    Try

        ctx = winID.Impersonate()
        Dim request As HttpWebRequest = CType(WebRequest.Create(p1), HttpWebRequest)


        request.UseDefaultCredentials = True
        request.Method = "GET"
        request.PreAuthenticate = True           
        request.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials
        Try

            webRes = CType(request.GetResponse(), HttpWebResponse)

        Catch ex As Exception 

        End Try
    Catch ex As Exception 

    Finally
        ctx.Undo()
    End Try
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