public ETagBasedCacheFilterAttribute(ETagDependencies dependencies)
     : this(null, dependencies)
 {
 }
 /// <summary>
 /// Initializes a new instance of the <see cref="ETagBasedCacheFilterAttribute" /> class.
 /// </summary>
 /// <param name="contentType">Type of the content.</param>
 /// <param name="dependencies">The dependencies.</param>
 public ETagBasedCacheFilterAttribute(string contentType, ETagDependencies dependencies)
     : base()
 {
     ContentType  = contentType ?? "text/plain";
     Dependencies = dependencies;
 }