VB.NET

Azure Blob - Get Tags (Check if Blob Exists)

See more Azure Cloud Storage Examples

Gets the user-defined tags for a specified blob. This can also be used as a way to check to see if a blob exists. VB.NET

Dim success As Boolean = False

' 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: Content-Length, x-ms-date, Authorization.  These headers
' are automatically set by Chilkat.

' The Azure blob container is "test", the file is "helloWorld.txt"
' Add "?comp=tags" to get the user-defined tags instead of the actual blob content.
Dim sb As New Chilkat.StringBuilder
success = rest.FullRequestNoBodySb("GET","/test/helloWorldajdfadf.txt?comp=tags",sb)
If (success = False) 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("---")
    Debug.WriteLine("LastRequestStartLine: " & rest.LastRequestStartLine)
    Debug.WriteLine("LastRequestHeader: " & rest.LastRequestHeader)
    Exit Sub
End If


' A typical blob with no tags will return this:

' <?xml version="1.0" encoding="utf-8"?>
' <Tags><TagSet/></Tags>

' If the blob does not exist, you get this:

' <?xml version="1.0" encoding="utf-8"?>
' <Error>
'     <Code>BlobNotFound</Code>
'     <Message>The specified blob does not exist.
' 	RequestId:fcfefdd9-301e-001a-2135-3a23d2000000
' 	Time:2023-02-06T14:17:00.7805577Z
'     </Message>
' </Error>

Debug.WriteLine(sb.GetAsString())

' To see if we got Tags or an Error, then examine the XML.
Dim xml As New Chilkat.Xml
xml.LoadSb(sb,True)

' Examine the tag..
If (xml.TagEquals("Tags") = True) Then
    Debug.WriteLine("Blob exists!")
Else

    If (xml.ChildContentMatches("Code","BlobNotFound",True) = True) Then
        Debug.WriteLine("Blob does not exist.")
    Else
        Debug.WriteLine("Some other error...")
    End If


End If


Debug.WriteLine("Success.")