Question

所以我需要从IotHub上传这个json文件到我的AzureBlob存储。到目前为止，我有一个存储帐户和一个链接到我的IoT HUb的容器。我有一个PCL项目，链接到3个平台项目（Android，iOS和UWP）。在我的PCL项目中，我有一个deviceClient，否则会发送遥测数据。

我尝试使用https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-csharp-csharp-file-upload

中的这段代码

private static async void SendToBlobAsync()
{
    string fileName = "data.json";
    Console.WriteLine("Uploading file: {0}", fileName);
    var watch = System.Diagnostics.Stopwatch.StartNew();

    using (var sourceData = new FileStream(@"image.jpg", FileMode.Open))
    {
        await deviceClient.UploadToBlobAsync(fileName, sourceData);
    }

    watch.Stop();
    Console.WriteLine("Time to upload file: {0}ms\n",batch.ElapsedMilliseconds);
}

但我没有得到方法＆＃34; UploadToBlobAsync＆＃34;关于智能感知。

我正在使用VS2017。

添加了NuGet包：Microsoft.Azure.Devices.Client.PCL

我的IOTHubHelper类引用了Microsoft.Azure.Devices.Client;

Answer 1

添加了NuGet包：Microsoft.Azure.Devices.Client.PCL

但我没有在IntelliSense上获得“UploadToBlobAsync”方法。

Microsoft.Azure.Devices.Client关于Azure/azure-iot-sdk-csharp的srouce代码DeviceClient.cs定义如下：

#if !PCL
        /// <summary>
        /// Uploads a stream to a block blob in a storage account associated with the IoTHub for that device.
        /// If the blob already exists, it will be overwritten.
        /// </summary>
        /// <param name="blobName"></param>
        /// <param name="source"></param>
        /// <returns>AsncTask</returns>
        public Task UploadToBlobAsync(String blobName, System.IO.Stream source)
        {
            if (String.IsNullOrEmpty(blobName))
            {
                throw Fx.Exception.ArgumentNull("blobName");
            }
            if (source == null)
            {
                throw Fx.Exception.ArgumentNull("source");
            }
            if (blobName.Length > 1024)
            {
                throw Fx.Exception.Argument("blobName", "Length cannot exceed 1024 characters");
            }
            if (blobName.Split('/').Count() > 254)
            {
                throw Fx.Exception.Argument("blobName", "Path segment count cannot exceed 254");
            }

            HttpTransportHandler httpTransport = null;

#if !WINDOWS_UWP
            //We need to add the certificate to the fileUpload httpTransport if DeviceAuthenticationWithX509Certificate
            if (this.Certificate != null)
            {
                Http1TransportSettings transportSettings = new Http1TransportSettings();
                transportSettings.ClientCertificate = this.Certificate;
                httpTransport = new HttpTransportHandler(null, iotHubConnectionString, transportSettings);
            }
            else
            {
                httpTransport = new HttpTransportHandler(iotHubConnectionString);
            }
#else 
            httpTransport = new HttpTransportHandler(iotHubConnectionString);
#endif
            return httpTransport.UploadToBlobAsync(blobName, source);
        }
#endif

注意： PCL库不支持UploadToBlobAsync功能。我假设您可以将PCL迁移到.NET标准库，并使用Microsoft.Azure.Devices.Client将文件上载到Azure Blob存储。此外，您可以按照tutorial关于使用.NET Standard构建Xamarin.Forms应用程序。

Answer 2

方法 Microsoft.Azure.Devices.Client.DeviceClient.UploadToBlobAsync 基本上是围绕通过Azure IoT Hub进行blob上载会话的REST API调用的包装器。此会话的顺序分为3个步骤，例如： 第1步。从Azure IoT Hub获取上载信息参考（打开会话） 第2步。根据收到的参考信息上传blob 第3步。关闭发布上传过程结果的会话。

以下代码段显示了在PCL项目中实现的上述步骤的示例：

    private async Task UploadToBlobAsync(string blobName, Stream source, string iothubnamespace, string deviceId, string deviceKey)
    {
        using(HttpClient client = new HttpClient())
        {
            // create authorization header
            string deviceSasToken = GetSASToken($"{iothubnamespace}.azure-devices.net/devices/{deviceId}", deviceKey, null, 1);
            client.DefaultRequestHeaders.Add("Authorization", deviceSasToken);

            // step 1. get the upload info
            var payload = JsonConvert.SerializeObject(new { blobName = blobName }); 
            var response = await client.PostAsync($"https://{iothubnamespace}.azure-devices.net/devices/{deviceId}/files?api-version=2016-11-14", new StringContent(payload, Encoding.UTF8, "application/json"));                
            var infoType = new { correlationId = "", hostName = "", containerName = "", blobName = "", sasToken = "" };
            var uploadInfo = JsonConvert.DeserializeAnonymousType(await response.Content.ReadAsStringAsync(), infoType);

            // step 2. upload blob
            var uploadUri = $"https://{uploadInfo.hostName}/{uploadInfo.containerName}/{uploadInfo.blobName}{uploadInfo.sasToken}";
            client.DefaultRequestHeaders.Add("x-ms-blob-type", "blockblob");
            client.DefaultRequestHeaders.Remove("Authorization");
            response = await client.PutAsync(uploadUri, new StreamContent(source));

            // step 3. send completed
            bool isUploaded = response.StatusCode == System.Net.HttpStatusCode.Created;
            client.DefaultRequestHeaders.Add("Authorization", deviceSasToken);
            payload = JsonConvert.SerializeObject(new { correlationId = uploadInfo.correlationId, statusCode = isUploaded ? 0 : -1, statusDescription = response.ReasonPhrase, isSuccess = isUploaded });
            response = await client.PostAsync($"https://{iothubnamespace}.azure-devices.net/devices/{deviceId}/files/notifications?api-version=2016-11-14", new StringContent(payload, Encoding.UTF8, "application/json"));
        }
    }

对于授权标头我们需要一个sasToken，因此以下代码片段显示了它的实现：

    private string GetSASToken(string resourceUri, string key, string keyName = null, uint hours = 24)
    {
        var expiry = Convert.ToString((int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds + 3600 * hours);
        string stringToSign = System.Net.WebUtility.UrlEncode(resourceUri) + "\n" + expiry;
        HMACSHA256 hmac = new HMACSHA256(Convert.FromBase64String(key));

        var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));
        var sasToken = keyName == null ?
            String.Format(CultureInfo.InvariantCulture, "SharedAccessSignature sr={0}&sig={1}&se={2}", System.Net.WebUtility.UrlEncode(resourceUri), System.Net.WebUtility.UrlEncode(signature), expiry) :
            String.Format(CultureInfo.InvariantCulture, "SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}", System.Net.WebUtility.UrlEncode(resourceUri), System.Net.WebUtility.UrlEncode(signature), expiry, keyName);
        return sasToken;
    }

请注意，上述实现并未处理步骤2中的重试机制。

如何通过IOT中心从Xamarin PCL项目将文件上传到azure Blob存储

2 个答案: