问题描述

通过.NET Azure Storage Blobs SDK , 获取Blob的MD5值，查看了Azure操作手册中，介绍可以使用 blob.Properties.ContentMD5 属性。

    //blob 文件测试
    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer container = blobClient.GetContainerReference("file");
    CloudBlockBlob blob = container.GetBlockBlobReference(@"image-03.jpg");
    blob.UploadFromFile(filePath1, FileMode.OpenOrCreate);
    Console.WriteLine("md5=" + blob.Properties.ContentMD5);

但是，在项目中，发现SDK更新后(Azure.Storage.Blobs 12.9.1)后，Properties中并没有ContentMD5属性？

image.png

问题解答

查看Blob Properties属性的源代码，发现没有了ContentMD5, 但是可以使用ContentHash。如果把ContentHash进行Base64编码后，它的结果就和Azure门户中的Content-MD5值一样：

image.png

示例代码如下：

        static async Task GetBlobMD5Async(string connectionString,string containerName)
        {
            //// Create a BlobServiceClient object which will be used to create a container client
            BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);
            BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(containerName);
 
            Console.WriteLine("Listing blobs...");
            // List all blobs in the container
            await foreach (BlobItem blobItem in containerClient.GetBlobsAsync())
            {
                Console.WriteLine("\t" + blobItem.Name);
 
                BlobClient bclient = containerClient.GetBlobClient(blobItem.Name);
 
                // Get the blob properties
                BlobProperties properties = await bclient.GetPropertiesAsync();
 
                // Display some of the blob's property values
                Console.WriteLine($"\t\t ContentLanguage: {properties.ContentLanguage}");
                Console.WriteLine($"\t\t ContentType: {properties.ContentType}");
                Console.WriteLine($"\t\t CreatedOn: {properties.CreatedOn}");
                Console.WriteLine($"\t\t LastModified: {properties.LastModified}");
                Console.WriteLine($"\t\t ContentHash: {FormatHashValue(properties.ContentHash)}");
                Console.WriteLine($"\t\t ContentMD5: {Convert.ToBase64String(properties.ContentHash)}");
            }
        }
 
        public static string FormatHashValue(byte[] contentHash)
        {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < contentHash.Length; i++)
            {
                sb.Append(contentHash[i].ToString("x2"));
            }
            return sb.ToString();
        }

参考资料

如何调用 API 获取 Azure File 存储中文件的 MD5值：https://docs.azure.cn/zh-cn/articles/azure-operations-guide/storage/aog-storage-blob-file-md5

BlobProperties.ContentHash Property: https://learn.microsoft.com/en-us/dotnet/api/azure.storage.blobs.models.blobproperties.contenthash?view=azure-dotnet

Manage blob properties and metadata with .NET ： https://learn.microsoft.com/en-us/azure/storage/blobs/storage-blob-properties-metadata#set-and-retrieve-properties

当在复杂的环境中面临问题，格物之道需：浊而静之徐清，安以动之徐生。 云中，恰是如此!