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POStreaming an Azure blob to the client asynchronously with .NET 4.5 async, await
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  1. POStreaming an Azure blob to the client asynchronously with .NET 4.5 async, await
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    copied!<p>I'm implementing my own async HTTP handler with <code>HttpTaskAsyncHandler</code> and using async &amp; await to keep it fully asynchronous.</p> <p>I want to stream an azure blob directly to the client. It's true that I can redirect the client to the blob URL and have them download it directly, but let's assume I don't want to do that (my blob is private for example).</p> <p>This is my current implementation:</p> <p><strong>Code:</strong></p> <pre><code> public async Task&lt;bool&gt; DownloadToStreamAsync(ICloudBlob blob, Stream stream) { bool blobFound = true; IAsyncResult asyncResult = blob.BeginDownloadToStream(stream, null, null); await Task.Factory.FromAsync(asyncResult, (r) =&gt; { try { blob.EndDownloadToStream(r); } catch (StorageException) { blobFound = false; } }); return blobFound; } </code></pre> <p><strong>Usage:</strong></p> <pre><code> public override async Task ProcessRequestAsync(HttpContext context) { CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageAccountConnectionString")); CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient(); CloudBlobContainer container = blobClient.GetContainerReference("container1"); CloudBlockBlob blockBlob = container.GetBlockBlobReference("blob1.txt"); await DownloadToStreamAsync(blockBlob, context.Response.OutputStream); } </code></pre> <p>Is this code indeed fully asynchronous and will free my HTTP server to handle other clients while the streaming takes place? (ie if I had a single server thread)</p> <p>Is it possible to keep the blobs compressed (GZIP) and have the client deflate them using <code>Content-Encoding: gzip</code>?</p> <p><strong>Update: (as of Storage 2.1.0.0 RC)</strong></p> <p>Async now supported natively.</p> <pre><code>CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageAccountConnectionString")); CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient(); CloudBlobContainer container = blobClient.GetContainerReference("container1"); CloudBlockBlob blockBlob = container.GetBlockBlobReference("blob1.txt"); await blockBlob.DownloadToStreamAsync(context.Response.OutputStream); </code></pre>
 

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