以下代码允许您使用您的 google drive api 凭据向用户请求登录信息，并将文件下载到您的服务器以执行一些请求：
Option Strict On
Option Explicit On
Imports System.Net
Imports System.IO
Imports System.Linq
Imports System.Threading
Imports System.Web
Imports System.Web.UI.WebControls
Imports Google
Imports Google.Apis.Auth.OAuth2
Imports Google.Apis.Auth.OAuth2.Flows
Imports Google.Apis.Auth.OAuth2.Web
Imports Google.Apis.Services
'for drive
Imports Google.Apis.Drive.v2
Imports Google.Apis.Drive.v2.Data
Imports Google.Apis.Util.Store
'for AuthorizationCodeRequestUrl
Imports Google.Apis.Auth.OAuth2.Requests
Imports System.Drawing
Public Class _Default
Inherits Page
Private redirect_uri As String = ""
Private client_id As String = ""
Private client_secret As String = ""
Private service As DriveService
'Application logic should manage users authentication.
'This sample works with only one user. You can change it by retrieving
'data from the session.
'You use the word user because you are authorized by the user to access
'their drive contents.
Private UserId As String = "user"
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
Dim SCOPES As String() = New [String]() {"https://www.googleapis.com/auth/drive", "https://www.googleapis.com/auth/userinfo.email", "https://www.googleapis.com/auth/userinfo.profile", "https://www.googleapis.com/auth/drive.install"}
Dim flow As GoogleAuthorizationCodeFlow
'use extended class to create google authorization code flow
'use custom own datastore
flow = New ForceOfflineGoogleAuthorizationCodeFlow(New GoogleAuthorizationCodeFlow.Initializer() With {
.DataStore = New FileDataStore("D:\inetpub\wwwroot\go\filedatastore", True),
.ClientSecrets = New ClientSecrets() With {
.ClientId = client_id,
.ClientSecret = client_secret
},
.Scopes = SCOPES
})
Dim uri = Request.Url.ToString()
Dim redirecturi As String = redirect_uri
Dim code = Request("code")
If code IsNot Nothing Then
output.Text &= "<br />Code: " & code & "<br />"
output.Text &= "<br />UserID: " & UserId & "<br />"
output.Text &= "<br />URI: " & uri & "<br />"
output.Text &= "<br />RedirectURI: " & redirecturi & "<br />"
output.Text &= "<br />uri-substring-thing: " & uri.Substring(0, uri.IndexOf("?")) & "<br />"
Dim token = flow.ExchangeCodeForTokenAsync(UserId, code, redirecturi, CancellationToken.None).Result
' Extract the right state.
Dim oauthState = AuthWebUtility.ExtracRedirectFromState(flow.DataStore, UserId, Request("state")).Result
Response.Redirect(oauthState)
Else
Dim result = New AuthorizationCodeWebApp(flow, redirecturi, uri).AuthorizeAsync(UserId, CancellationToken.None).Result
If result.RedirectUri IsNot Nothing Then
' Redirect the user to the authorization server.
Response.Redirect(result.RedirectUri)
Else
' The data store contains the user credential, so the user has been already authenticated.
service = New DriveService(New BaseClientService.Initializer() With {
.HttpClientInitializer = result.Credential,
.ApplicationName = "Drive API Sample"
})
End If
End If
End Sub
''' <summary>
''' Download a file
''' Documentation: https://developers.google.com/drive/v2/reference/files/get
''' </summary>
''' <param name="_service">a Valid authenticated DriveService</param>
''' <param name="_fileResource">File resource of the file to download</param>
''' <param name="_saveTo">location of where to save the file including the file name to save it as.</param>
''' <returns></returns>
Public Shared Function downloadFile(_service As DriveService, _fileResource As Data.File, _saveTo As String) As [Boolean]
If Not [String].IsNullOrEmpty(_fileResource.DownloadUrl) Then
Try
Dim x = _service.HttpClient.GetByteArrayAsync(_fileResource.DownloadUrl)
Dim arrBytes As Byte() = x.Result
System.IO.File.WriteAllBytes(_saveTo, arrBytes)
Return True
Catch e As Exception
Console.WriteLine("An error occurred: " + e.Message)
Return False
End Try
Else
' The file doesn't have any content stored on Drive.
Return False
End If
End Function
Public Async Function GetFile(IncomingFileID As String) As Tasks.Task
Try
Dim request As FilesResource.GetRequest = service.Files.Get(IncomingFileID)
Dim response As Data.File = Await request.ExecuteAsync(CancellationToken.None)
downloadFile(service, response, "D:/inetpub/wwwroot/go/" & Guid.NewGuid.ToString)
Catch ex As Exception
Dim str As String = "<br />" & ex.ToString()
str = str.Replace(Environment.NewLine, Environment.NewLine + "<br/>")
str = str.Replace(" ", " ")
output.Text &= String.Format("<font color=""red"">{0}</font>", str)
End Try
End Function
'''<summary>Gets the File Lists of the user.</summary>
Public Async Function FetchFilelists() As System.Threading.Tasks.Task
Try
' Get all files of the user asynchronously.
Dim request As FilesResource.ListRequest = service.Files.List()
'get only my files
request.Q = "mimeType contains 'image/'"
Dim response As FileList = Await request.ExecuteAsync()
ShowFilelists(response)
Catch ex As Exception
Dim str = ex.ToString()
str = str.Replace(Environment.NewLine, Environment.NewLine + "<br/>")
str = str.Replace(" ", " ")
output.Text = String.Format("<font color=""red"">{0}</font>", str)
End Try
End Function
Private Sub ShowFilelists(response As FileList)
If response.Items Is Nothing Then
output.Text &= "You have no files!<br/>"
Return
End If
output.Text &= "Showing files...<br/>"
Dim ctr As Integer = 0
For Each file As Google.Apis.Drive.v2.Data.File In response.Items
ctr += 1
Dim listPanel As New Panel() With {
.BorderWidth = Unit.Pixel(1),
.BorderColor = Color.Black
}
listPanel.Controls.Add(New Label() With {
.Text = file.Title + "--" + file.MimeType
})
listPanel.Controls.Add(New Label() With {
.Text = "<hr/>"
})
If file.MimeType.ToString().Contains("folder") = False Then
listPanel.Controls.Add(New HyperLink() With {
.Text = "Download",
.NavigateUrl = file.WebContentLink
})
listPanel.Controls.Add(New Button() With {
.Text = "Use This Image", .OnClientClick = "document.getElementById('currentImageId').value = '" & file.Id & "';return false;"})
End If
lists.Controls.Add(listPanel)
Next
output.Text &= "Total Files: " & ctr.ToString
End Sub
Protected Async Sub listButton_Click(sender As Object, e As EventArgs) Handles listbutton.Click
Await FetchFilelists()
End Sub
Protected Async Sub DownloadImageButton_Click(sender As Object, e As EventArgs) Handles DownloadImageButton.Click
Dim idToUse As String = Page.Request.Form(currentImageId.UniqueID)
output.Text &= "<br />Attempting to download id: " & idToUse & "<br />"
Await GetFile(idToUse)
output.Text &= "<br />Download Completed<br />"
End Sub
'overwrite. force offline.
Friend Class ForceOfflineGoogleAuthorizationCodeFlow
Inherits GoogleAuthorizationCodeFlow
'source: //gotoanswer.stanford.edu/google_analytics_oauth_with_accesstype__offline_in_c-4478263/
Public Sub New(initializer As GoogleAuthorizationCodeFlow.Initializer)
MyBase.New(initializer)
End Sub
Public Overrides Function CreateAuthorizationCodeRequest(redirectUri As String) As AuthorizationCodeRequestUrl
Dim ss = New Google.Apis.Auth.OAuth2.Requests.GoogleAuthorizationCodeRequestUrl(New Uri(AuthorizationServerUrl))
ss.AccessType = "offline"
ss.ApprovalPrompt = "force"
ss.ClientId = ClientSecrets.ClientId
ss.Scope = String.Join(" ", Scopes)
ss.RedirectUri = redirectUri
Return ss
End Function
End Class
End Class
这是 WebForm .aspx 页面：
<%@ Page Title="Home Page" Language="VB" MasterPageFile="~/Site.Master"
AutoEventWireup="true" CodeBehind="Default.aspx.vb" Inherits="PictureMyCard._Default" Async="True" %>
<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent"
runat="server">
<div>
<asp:Button ID="listbutton" runat="server" ClientIDMode="Static" Text="list" />
<asp:Label id="output" runat="server" ClientIDMode="Static" Text="..." ></asp:Label>
</div>
<asp:Label ID="lists" ClientIDMode="Static" Text="..." runat="server"></asp:Label>
<hr />
<asp:HiddenField ClientIDMode="Static" ID="currentImageId" runat="server" />
<asp:Button runat="server" ID="DownloadImageButton" ClientIDMode="Static" Text="Download Image to server" />
</asp:Content>