azure cdn image tag helper

cdnimage-taghelper.cs

if (AppendVersion) 
{
    EnsureFileVersionProvider();
    Src = output.Attributes[SrcAttributeName].Value as string; 
 	// Check if the CDN Base URI is set and add to the src attribute 
	if (!string.IsNullOrWhiteSpace(CdnUri)) 
	{ 
  		output.Attributes.SetAttribute(SrcAttributeName, string.Format("{0}{1}", CdnUri, _fileVersionProvider.AddFileVersionToPath(Src))); 
    } 
}