// Set the If-Match condition to the original ETag.
        BlobUploadOptions blobUploadOptions = new BlobUploadOptions()
        {
            Conditions = new BlobRequestConditions()
            {
                IfMatch = originalETag
            }
        };

BlobLeaseClient blobLeaseClient = blobClient.GetBlobLeaseClient();

// Acquire a lease on the blob. 
BlobLease blobLease = await blobLeaseClient.AcquireAsync(TimeSpan.FromSeconds(15));

// Set the request condition to include the lease ID.
        BlobUploadOptions blobUploadOptions = new BlobUploadOptions()
        {
            Conditions = new BlobRequestConditions()
            {
                LeaseId = blobLease.LeaseId
            }
        };

private static async Task DemonstrateOptimisticConcurrencyBlob(BlobClient blobClient)
{
    Console.WriteLine("Demonstrate optimistic concurrency");

    BlobContainerClient containerClient = blobClient.GetParentBlobContainerClient();

    try
    {
        // Create the container if it does not exist.
        await containerClient.CreateIfNotExistsAsync();

        // Upload text to a new block blob.
        string blobContents1 = "First update. Overwrite blob if it exists.";
        byte[] byteArray = Encoding.ASCII.GetBytes(blobContents1);

        ETag originalETag;
        
        using (MemoryStream stream = new MemoryStream(byteArray))
        {
            // 从 Azure 存储检索 blob。 响应包括用于标识对象的当前版本的 HTTP ETag 标头值。
            BlobContentInfo blobContentInfo = await blobClient.UploadAsync(stream, overwrite: true);
            originalETag = blobContentInfo.ETag;
            Console.WriteLine("Blob added. Original ETag = {0}", originalETag);
        }

        // This code simulates an update by another client.
        // No ETag was provided, so original blob is overwritten and ETag updated.
        string blobContents2 = "Second update overwrites first update.";
        byteArray = Encoding.ASCII.GetBytes(blobContents2);

        using (MemoryStream stream = new MemoryStream(byteArray))
        {
            BlobContentInfo blobContentInfo = await blobClient.UploadAsync(stream, overwrite: true);
            Console.WriteLine("Blob updated. Updated ETag = {0}", blobContentInfo.ETag);
        }

        // Now try to update the blob using the original ETag value.
        string blobContents3 = "Third update. If-Match condition set to original ETag.";
        byteArray = Encoding.ASCII.GetBytes(blobContents3);

        // Set the If-Match condition to the original ETag.
        
        // 在更新 blob 时，应将在步骤 1 中获得的 ETag 值包括在写入请求的 If-Match 条件标头中。 Azure 存储会将请求中的 ETag 值与 blob 当前的 ETag 值进行比较。
        BlobUploadOptions blobUploadOptions = new BlobUploadOptions()
        {
            Conditions = new BlobRequestConditions()
            {
                IfMatch = originalETag
            }
        };

        using (MemoryStream stream = new MemoryStream(byteArray))
        {
            // This call should fail with error code 412 (Precondition Failed).
            //如果 blob 当前的 ETag 值不同于请求中提供的 If-Match 条件标头中指定的 ETag 值，则 Azure 存储会返回 HTTP 状态代码412（“不满足前提条件”）。 此错误向客户端表明，另一进程在客户端首先检索 blob 后已更新该 blob。
            //如果 blob 的当前 ETag 值与请求的 If-Match 条件标头中的 ETag 的版本相同，则 Azure 存储会执行请求的操作，并更新该 blob 的当前 ETag 值。
            BlobContentInfo blobContentInfo = await blobClient.UploadAsync(stream, blobUploadOptions);
        }
    }
    catch (RequestFailedException e)
    {
        if (e.Status == (int)HttpStatusCode.PreconditionFailed)
        {
            Console.WriteLine(
                @"Precondition failure as expected. Blob's ETag does not match ETag provided.");
        }
        else
        {
            Console.WriteLine(e.Message);
            throw;
        }
    }
}