如何允许覆盖 ASP.NET Core 应用程序中的 blob？

Question

用户可以在创建记录时上传图像，当您编辑该记录并尝试上传新图像时，会出现“此 blob 已存在”错误。有没有办法可以在我的应用程序中启用同名 blob 的覆盖？

这是我处理更新过程的代码。

值得注意的是，为了应用程序，我创建了图像的三个迭代，因此我包含了包含该信息的数组。

CarController.cs

private readonly int[] sizeArray = new int[] { 700, 350, 150 };

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(Car car)
{
    if (ModelState.IsValid)
    {
        //Create the Car
                _carService.InsertCar(car);

                //Get the ID of the newly created car
                int id = car.Id;

                //Define the container name for Azure Storage
                string strContainerName = "uploads";                               

                //Blob Client
                BlobServiceClient blobServiceClient = new BlobServiceClient(accessKey);
                BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(strContainerName);

                //Iterate over the array of image sizes
                foreach (var imageSize in sizeArray)
                {
                    try
                    {
                        //Pass image to image processor and save to the blob location
                        string fileName = "car/" + id + "/car-image-" + imageSize + ".jpg";
                        Stream returnStream = ProcessImage(imageSize, car);
                        containerClient.UploadBlob(fileName, returnStream);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine(ex.Message);
                    }
                }                   
                return RedirectToAction(nameof(Index));
            }            
            return View(car);
        }

Answer 1

我认为您正在使用v12 客户端库。

那么容器级别没有blob覆盖方法，你应该Upload(Stream content, bool overwrite = false)使用BlobClient. 示例代码如下：

            BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);
            BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(mycontainer);
            BlobClient blobClient = containerClient.GetBlobClient("blob_name");

            blobClient.Upload(your_stream, overwrite: true);

Answer 2

如果你想同时指定两者overwrite: true并使用，这是带有参数的重载的实现：BlobStorageOptionsUpload(...)bool overwrite

public virtual Response<BlobContentInfo> Upload(
    Stream content,
    bool overwrite = false,
    CancellationToken cancellationToken = default) =>
    Upload(
        content,
        conditions: overwrite ? null : new BlobRequestConditions { IfNoneMatch = new ETag(Constants.Wildcard) },
        cancellationToken: cancellationToken);

这会导致以下重载（为简洁起见，省略了一些代码）：

public virtual Response<BlobContentInfo> Upload(
    ....
    BlobRequestConditions conditions = default,
    ....) =>
    StagedUploadInternal(
        content,
        new BlobUploadOptions
        {
            ...
            Conditions = conditions,
            ...
        },
        ...

overwrite因此，只要您在BlobUploadOptions没有任何特定选项的情况下指定自己的值，实际上就是默认值IfNoneMatch。

该函数的注释也支持了这一点：

// Summary:
//     The Azure.Storage.Blobs.BlobClient.UploadAsync(System.IO.Stream,Azure.Storage.Blobs.Models.BlobUploadOptions,System.Threading.CancellationToken)
//     operation overwrites the contents of the blob, creating a new block blob if none
//     exists. Overwriting an existing block blob replaces any existing metadata on
//     the blob. Set access conditions through Azure.Storage.Blobs.Models.BlobUploadOptions.Conditions
//     to avoid overwriting existing data.

代码复制自BlobClient.cs.