using Microsoft.WindowsAzure.Storage;
using System.IO;

var account = CloudStorageAccount.Parse("YourStorageConnectionString");
var client = account.CreateCloudBlobClient();
var container = client.GetContainerReference(GetAzureContainerByFileType(type));
var blob = container.GetBlockBlobReference("myphoto.jpg");

blob.Properties.ContentType = "image/jpeg";

blob.SetProperties();