Add a TryResolve method for dependencies

--HG--
branch : dev

src/Orchard.Tests/DisplayManagement/DefaultDisplayManagerTests.cs

@@ -106,6 +106,10 @@ namespace Orchard.Tests.DisplayManagement {
                 throw new NotImplementedException();
             }
 
+            public override bool TryResolve<T>(out T service) {
+                throw new NotImplementedException();
+            }
+
             public override T GetState<T>(string name) {
                 object value;
                 return _state.TryGetValue(name, out value) ? (T)value : default(T);

src/Orchard/Environment/DefaultWorkContextAccessor.cs

@@ -95,6 +95,10 @@ namespace Orchard.Environment {
                 return _componentContext.Resolve<T>();
             }
 
+            public override bool TryResolve<T>(out T service) {
+                return _componentContext.TryResolve(out service);
+            }
+
             public override T GetState<T>(string name) {
                 var resolver = _stateResolvers.GetOrAdd(name, FindResolverForState<T>);
                 return (T)resolver();
@@ -141,6 +145,10 @@ namespace Orchard.Environment {
             public TService Resolve<TService>() {
                 return WorkContext.Resolve<TService>();
             }
+
+            public bool TryResolve<TService>(out TService service) {
+                return WorkContext.TryResolve(out service);
+            }
         }
 
         class ThreadStaticScopeImplementation : IWorkContextScope {
@@ -168,6 +176,10 @@ namespace Orchard.Environment {
             public TService Resolve<TService>() {
                 return WorkContext.Resolve<TService>();
             }
+
+            public bool TryResolve<TService>(out TService service) {
+                return WorkContext.TryResolve(out service);
+            }
         }
     }
 }

src/Orchard/IWorkContextAccessor.cs

@@ -17,5 +17,6 @@ namespace Orchard {
     public interface IWorkContextScope : IDisposable {
         WorkContext WorkContext { get; }
         TService Resolve<TService>();
+        bool TryResolve<TService>(out TService service);
     }
 }

src/Orchard/WorkContext.cs

@@ -6,6 +6,7 @@ using Orchard.Themes;
 namespace Orchard {
     public abstract class WorkContext {
         public abstract T Resolve<T>();
+        public abstract bool TryResolve<T>(out T service);
 
         public abstract T GetState<T>(string name);
         public abstract void SetState<T>(string name, T value);