VB.NET

Azure Storage: CORS Preflight Blob Request

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Azure Storage Blob Service REST API: Sample code to send a CORS pre-flight blob request. VB.NET

Dim success As Boolean = False

' Azure Blob Service Example: CORS Preflight Blob Request
' See also: https://msdn.microsoft.com/en-us/library/azure/dn535599.aspx

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim rest As New Chilkat.Rest

' Connect to the Azure Storage Blob Service
Dim bTls As Boolean = True
Dim port As Integer = 443
Dim bAutoReconnect As Boolean = True
' In this example, the storage account name is "chilkat".
success = rest.Connect("chilkat.blob.core.windows.net",port,bTls,bAutoReconnect)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' Provide Azure Cloud credentials for the REST call.
Dim azAuth As New Chilkat.AuthAzureStorage
azAuth.AccessKey = "AZURE_ACCESS_KEY"
' The account name used here should match the 1st part of the domain passed in the call to Connect (above).
azAuth.Account = "chilkat"
azAuth.Scheme = "SharedKey"
azAuth.Service = "Blob"
' This causes the "x-ms-version: 2021-08-06" header to be automatically added.
azAuth.XMsVersion = "2021-08-06"
success = rest.SetAuthAzureStorage(azAuth)

' Note: The application does not need to explicitly set the following
' headers: x-ms-date, Authorization.  These headers
' are automatically set by Chilkat.

' The preflight blob request requires the following two HTTP headers.
' The Origin is the domain from which the actual request will be issued.
success = rest.AddHeader("Origin","www.contoso.com")
' The Access-Control-Request-Method is the HTTP method (such as GET, POST, PUT, etc.) of the actual request.
success = rest.AddHeader("Access-Control-Request-Method","PUT")

' The expected response is a 202 response status code with no response body.
' The name of the container or blob resource in this example is "test". (Replace "test" with your container name.)
Dim responseStr As String = rest.FullRequestNoBody("OPTIONS","/test")
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' When successful, the Azure Storage service will respond with a 200 response code,
' with no response body.

' If CORS is not enabled or no matching rule is found for the request, 
' then a 403 status code is returned, with the following status text:
' "CORS not enabled or no matching rule found for this request."
If (rest.ResponseStatusCode <> 200) Then
    ' Examine the request/response to see what happened.
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)
    Debug.WriteLine("response body (if any): " & responseStr)
    Debug.WriteLine("---")
    Debug.WriteLine("LastRequestStartLine: " & rest.LastRequestStartLine)
    Debug.WriteLine("LastRequestHeader: " & rest.LastRequestHeader)
    Exit Sub
End If


Debug.WriteLine("Success: Preflight Blob Request is accepted.")