I see you're using the 1.7 SDK. This is a small encoding issue with the SDK which is also present in v2.0. Let's see what happens.
No encoding
account.CreateCloudBlobClient()
.GetContainerReference("temp")
.GetBlobReference("abc[]def.txt")
.UploadFile("myfile.txt");
If you don't encode the blob name, you'll end up with a request to the following URL which is causing the authentication exception:
The is because the SDK uses Uri.EscapeUriString
internally to encode your string, but this doesn't take into account square brackets.
Encoding
Then you would expect the following to do the trick:
account.CreateCloudBlobClient()
.GetContainerReference("temp")
.GetBlobReference(HttpUtility.UrlEncode("abc[]def.txt"))
.UploadFile("myfile.txt");
The issue here is that you'll end up with this url:
http://account.blob.core.windows.net/temp/abc%255b%255ddef.txt
So what's happening here? Calling HttpUtility.UrlEncode turns abc[]def.txt to abc%5B%5Ddef.txt, which is correct. But internally, the SDK will encode this string again which results in abc%255b%255ddef.txt, which isn't what you want.
Workaround
The only way to apply encoding which takes square brackets into accounts is by using a small workaround. If you pass the full URL to the GetBlobReference method, the SDK assumes you did all the encoding yourself:
var container = account.CreateCloudBlobClient().GetContainerReference("temp");
var blob = container.GetBlobReference(String.Format("{0}/{1}",
container.Uri, System.Web.HttpUtility.UrlEncode("abc[]def.txt")));
blob.UploadFile("myfile.txt");
This results in a correctly encoded URL:
http://account.blob.core.windows.net/temp/abc%5b%5ddef.txt
And if you use a tool like CloudXplorer, you'll see the blob with the correct filename: