c# - 在 foreach 循环之外使用 IEnumerable 列表

Question

我正在使用 IEnumerable在 for each 循环中，如下所示:

foreach (IListBlobItem blobItem in container.ListBlobs())
{        
    if (blobItem is CloudBlobDirectory)
    {
        CloudBlobDirectory directory = (CloudBlobDirectory)blobItem;
        IEnumerable<IListBlobItem> blobs = directory.ListBlobs(true);
    }                
}
await ProcessBlobs(blobs);

我想使用 blobs此 foreach 循环之外的变量，但我收到此消息:blobs doesnot exist in the current context

我决定定义 blobs在 foreach 循环之外:

IEnumerable<IListBlobItem> blobs = new IEnumerable<IListBlobItem>;

foreach (IListBlobItem blobItem in container.ListBlobs())
{           
    if (blobItem is CloudBlobDirectory)
    {
        //Console.WriteLine(blobItem.Uri);
        CloudBlobDirectory directory = (CloudBlobDirectory)blobItem;
        IEnumerable<IListBlobItem> blobs = directory.ListBlobs(true);                    
    }
}

但我收到错误:can not create an instance of the abstract class or interface IEnumerable<IListBlobItem>

你知道我该如何解决这个问题吗？

Answer 1

您可以将 blob 声明为一个空集合，例如数组:

   // Empty
   IEnumerable<IListBlobItem> blobs = new IListBlobItem[0];

   foreach (IListBlobItem blobItem in container.ListBlobs())
   {
      if (blobItem is CloudBlobDirectory)
      {
          CloudBlobDirectory directory = (CloudBlobDirectory)blobItem;
          blobs = directory.ListBlobs(true);                    
      }            
   }

   // process either blobs from foreach or an empty collection
   await ProcessBlobs(blobs);