使用 MemoryStream 和 WebApi 返回图像

Question

我正在尝试使端点 return 成为包含图像的 MemoryStream。

这是我目前的代码：

控制器端点：

[Route("v1/consumer/profile-image")]
[HttpGet]
public async Task<HttpResponseMessage> GetProfileImage(string id)
{
    var result = await ImageService.GetImage(true, id);

    var response = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new StreamContent(result.BlobStream)
    };

    response.Content.Headers.ContentType = new MediaTypeHeaderValue(result.ContentType);

    return response;
}

服务方式：

public async Task<ImageStream> GetImage(string profileId)
{
    var imageStream = new MemoryStream();

    var account = CloudStorageAccount.Parse(ConnectionString);
    var client = account.CreateCloudBlobClient();

    CloudBlobContainer container;
    CloudBlockBlob blob = null;

    container = client.GetContainerReference(ConsumerImageContainer);
    blob = container.GetBlockBlobReference(profileId);

    blob.FetchAttributes();

    blob.DownloadToStream(imageStream);

    return new ImageStream
    {
        BlobStream = imageStream,
        ContentType = blob.Properties.ContentType
    };
}

public class ImageStream
{
    public MemoryStream BlobStream { get; set; }
    public string ContentType { get; set; }
}

我的问题是我似乎没有取回任何内容 - 我可以看到内容类型设置正确，但图像没有设置：

Request Headers

Request URL: https://localhost:44347/v1/consumer/profile-image
Request Method: GET
Status Code: 200 
Remote Address: [::1]:44347
Referrer Policy: no-referrer-when-downgrade

Response Headers

access-control-allow-origin: *
content-length: 0
content-type: image/jpeg
date: Mon, 09 Jul 2018 13:38:58 GMT
server: Microsoft-IIS/10.0
status: 200
x-powered-by: ASP.NET
x-sourcefiles: =?UTF-8?B?QzpcVXNlcnNcTWljaGFlbCBSeWFuXERvY3VtZW50c1xDb25zdW1lckFQSVxPcHRlemkuQ29uc3VtZXJBcGlcdjFcY29uc3VtZXJccHJvZmlsZS1pbWFnZQ==?=

Answer 1

我需要在返回之前重置流位置：

blob.FetchAttributes();

blob.DownloadToStream(imageStream);

imageStream.Position = 0;

return new ImageStream
{
    BlobStream = imageStream,
    ContentType = blob.Properties.ContentType
};