Added a better message than - The operation is not ready for invocati…

…on. - like what and who

src/OpenRasta/OperationModel/MethodBased/MethodBasedOperation.cs

@@ -53,7 +53,10 @@ public IEnumerable<T> FindAttributes<T>() where T : class
         public IEnumerable<OutputMember> Invoke()
         {
             if (!Inputs.AllReady())
-                throw new InvalidOperationException("The operation is not ready for invocation.");
+            {
+                var notReady = Inputs.WhosNotReady();
+                throw new InvalidOperationException(string.Format("The operation {0} for {1} is not ready for invocation. These members are not ready; {2}", _method.Name, _method.Owner.Name, notReady.Select(x => x.Name).JoinString(", ")));
+            }
 
             var handler = CreateInstance(_ownerType, Resolver);
 

src/OpenRasta/OperationModel/OperationExtensions.cs

@@ -1,6 +1,8 @@
 using System.Collections.Generic;
 using System.Linq;
 
+using OpenRasta.TypeSystem;
+
 namespace OpenRasta.OperationModel
 {
     public static class OperationExtensions
@@ -10,7 +12,12 @@ public static bool AllReady(this IEnumerable<InputMember> members)
             return members.All(x => x.IsReadyForAssignment);
         }
 
-        /// <summary>
+        public static IEnumerable<IMember> WhosNotReady(this IEnumerable<InputMember> members)
+        {
+            return members.Where(x => x.IsReadyForAssignment == false).Select(x => x.Member);
+        }
+
+    /// <summary>
         /// Returns the number of members ready for invocation (aka either having a default value or having had a value assigned to them).
         /// </summary>
         /// <param name="members"></param>