(VB.NET) Download a SharePoint File by Path using HttpCurl

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This example shows how to use Chilkat's HttpCurl class to download a file from SharePoint when the file path within the document library is already known. The example uses Microsoft Graph to automatically resolve the SharePoint site name to a site ID, find the drive ID for the Documents document library, and then download the file directly by path using the Graph root:/path:/content syntax.

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Dim success As Boolean = False

' This example downloads a file from a SharePoint Documents document library
' when the file's path within the library is already known.
' 
' The file downloaded in this example is:
' 
'   images/sea_creatures/starfish.jpg
' 
' Unlike the previous example  that searched for a file by name and obtained
' its Microsoft Graph item ID, this example uses the Graph path-based API.
' 
' The example demonstrates how HttpCurl automatically resolves:
' 
'   site_name  -> site_id
'   site_id    -> document_library_id
' 
' and then uses the known file path to download the file directly.

success = False

' --------------------------------------------------------------------------------------------------------
' Before running this example, create an Azure App Registration and grant it
' the Microsoft Graph permissions required to access SharePoint.
' 
' The application will authenticate using OAuth2 Client Credentials.
' See:
' How to Create SharePoint App Registration for OAuth 2.0 Client Credentials
' --------------------------------------------------------------------------------------------------------

' Build a JSON authentication configuration.
' HttpCurl will use this information to automatically obtain OAuth2 access tokens.
Dim jsonAuth As New Chilkat.JsonObject

' Enable secret lookup.
' 
' Instead of hard-coding sensitive values such as the client ID,
' client secret, and token endpoint, secret specification strings
' are used.  Chilkat automatically retrieves the actual values from
' Windows Credential Manager (Windows) or Apple Keychain (macOS).
' 
' See:
' Secret Specification Strings
jsonAuth.EnableSecrets = True

success = jsonAuth.UpdateString("oauth2.client_id","!!sharepoint|oauth2|client_id")
If (success = True) Then
    success = jsonAuth.UpdateString("oauth2.client_secret","!!sharepoint|oauth2|client_secret")
End If

If (success = True) Then
    success = jsonAuth.UpdateString("oauth2.token_endpoint","!!sharepoint|oauth2|token_endpoint")
End If

If (success = False) Then
    Debug.WriteLine(jsonAuth.LastErrorText)
    Exit Sub
End If


' Request Microsoft Graph permissions that were granted to the application.
jsonAuth.UpdateString("oauth2.scope","https://graph.microsoft.com/.default")

' ---------------------------------------------------------------------------------------------------

Dim curl As New Chilkat.HttpCurl

' Associate the OAuth2 configuration with HttpCurl.
' 
' When the request is executed, Chilkat automatically obtains an access token
' if needed and adds the Authorization: Bearer header to the HTTP request.
curl.SetAuth(jsonAuth)

' Define values that are already known.
' 
' These variables are referenced in curl commands using
' {{variable_name}} substitution syntax.
curl.SetVar("sharepoint_hostname","example.sharepoint.com")
curl.SetVar("site_name","test")

' The download request requires a Microsoft Graph site ID.
' 
' Because the application only knows the SharePoint site name,
' define a helper function that can retrieve the site information.
curl.AddFunction("getSite","GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}")

' Extract the site's ID and store it in the HttpCurl variable named site_id.
curl.AddOutput("getSite","id","site_id")

' The download request also requires the drive ID of the Documents
' document library.
' 
' Microsoft Graph refers to document libraries as "drives".
curl.AddFunction("getDrives","GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives")

' Search the returned drives for the one named "Documents"
' and save its drive ID in the document_library_id variable.
curl.AddOutput2("getDrives","value","name","Documents",True,"id","document_library_id")

' This is the target Microsoft Graph request.
' 
' GET /sites/{site-id}/drives/{drive-id}/root:/{path-to-file}:/content
' 
' The path-based API allows a file to be downloaded directly when its
' location within the document library is known.
' 
' The -L option causes HttpCurl to follow redirects.
' Microsoft Graph typically returns a redirect to the actual download URL.
' 
' The -o option specifies the output filename.
' The --output-dir option specifies the directory where the downloaded
' file will be saved.
Dim curlCommand As String = "GET -L --output-dir c:/temp/qa_output -o starfish.jpg https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root:/images/sea_creatures/starfish.jpg:/content"

' Execute the request.
' 
' HttpCurl examines the target request and determines that both
' site_id and document_library_id are required.
' 
' To obtain these values, it automatically builds and executes
' the following dependency chain:
' 
'   1) getSite    -> site_id
'   2) getDrives  -> document_library_id
'   3) download   -> file content
' 
' The file is streamed directly to the output file specified by
' the curl command.
success = curl.DoYourThing(curlCommand)
If (success = False) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


' A successful Graph response should return HTTP 200.
' Any other status code typically indicates an authentication,
' permission, site lookup, document library lookup, or file lookup error.
Dim statusCode As Integer = curl.StatusCode
If (statusCode <> 200) Then
    Debug.WriteLine(curl.ResponseBodyStr)
    Debug.WriteLine("status code = " & statusCode)
    Exit Sub
End If


' The file has been downloaded successfully and written to:
' 
'   c:/temp/qa_output/starfish.jpg
' 
Debug.WriteLine("Success.")