mcs/class/System.Web.Mvc3/Mvc/SingleServiceResolver.cs

   1 namespace System.Web.Mvc {
   2     using System.Globalization;
   3     using System.Web.Mvc.Resources;
   4
   5     internal class SingleServiceResolver<TService> : IResolver<TService> where TService : class {
   6
   7         private TService _currentValueFromResolver;
   8         private Func<TService> _currentValueThunk;
   9         private TService _defaultValue;
  10         private Func<IDependencyResolver> _resolverThunk;
  11         private string _callerMethodName;
  12
  13         public SingleServiceResolver(Func<TService> currentValueThunk, TService defaultValue, string callerMethodName) {
  14             if (currentValueThunk == null) {
  15                 throw new ArgumentNullException("currentValueThunk");
  16             }
  17             if (defaultValue == null) {
  18                 throw new ArgumentNullException("defaultValue");
  19             }
  20
  21             _resolverThunk = () => DependencyResolver.Current;
  22             _currentValueThunk = currentValueThunk;
  23             _defaultValue = defaultValue;
  24             _callerMethodName = callerMethodName;
  25         }
  26
  27         internal SingleServiceResolver(Func<TService> staticAccessor, TService defaultValue, IDependencyResolver resolver, string callerMethodName)
  28             : this(staticAccessor, defaultValue, callerMethodName) {
  29             if (resolver != null) {
  30                 _resolverThunk = () => resolver;
  31             }
  32         }
  33
  34         public TService Current {
  35             get {
  36                 if (_resolverThunk != null) {
  37                     lock (_currentValueThunk) {
  38                         if (_resolverThunk != null) {
  39                             _currentValueFromResolver = _resolverThunk().GetService<TService>();
  40                             _resolverThunk = null;
  41
  42                             if (_currentValueFromResolver != null && _currentValueThunk() != null) {
  43                                 throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, MvcResources.SingleServiceResolver_CannotRegisterTwoInstances, typeof(TService).Name.ToString(), _callerMethodName));
  44                             }
  45                         }
  46                     }
  47                 }
  48                 return _currentValueFromResolver ?? _currentValueThunk() ?? _defaultValue;
  49             }
  50         }
  51     }
  52 }