How do I Open A File Asynchronously in C#

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C#

.NET

C#4.0

asynchronous

.NET4.5

, +

What is the best way to execute file opening asynchronously even before copying begins. The exception I get is that the file is not accessible because its being used by another process.My code is shown below:

try
               {
                   using (var sourceStream = new FileStream(pathToDownloadedMedia, FileMode.Open, FileAccess.Read, FileShare.None, bufferSize: 4096, useAsync: true))
                   {
                       using (var destinationStream = File.Create(pathToProcessedMedia))
                       {
                           await sourceStream.CopyToAsync(destinationStream);
                       }
                   }
               }
               catch (Exception)
               {
                   throw new ApplicationException();
               }