Implemented "FromAttribute" for component parameters

samples/ClientServerApp/ClientServerApp.Client/CounterDisplay.cshtml

@@ -6,14 +6,10 @@
 </div>
 
 @functions {
-    // It would be cleaner if we could mark properties with [FromAttribute] or similar,
-    // instead of having to extract them from a dictionary manually.
-    private int currentCount;
-    private Action resetCounterCallback;
 
-    protected override void ReceiveParameters(IDictionary<string, object> parameters)
-    {
-        currentCount = (int)parameters["current-count"];
-        resetCounterCallback = (Action)parameters["on-reset"];
-    }
+    [FromAttribute("current-count")]
+    private int currentCount { get; set; }  //works with properties
+
+    [FromAttribute("on-reset")]
+    private Action resetCounterCallback;    //and fields
 }

samples/ClientServerApp/ClientServerApp.Client/_ViewImports.cshtml

@@ -4,5 +4,6 @@
 @using Task = Blazor.Runtime.FakeBcl.Task; // Temporary until Mono supports Task
 @using HttpClient = Blazor.Runtime.FakeBcl.HttpClient; // Temporary until Mono supports HttpClient
 @using ClientServerApp.Client
+@using Blazor.Runtime.Components
 @using ClientServerApp.Shared
 @using System.Net.Http

src/Blazor.Runtime/Components/FromAttributeAttribute.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Blazor.Runtime.Components
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+    public class FromAttributeAttribute : Attribute
+    {
+        public string AttributeName {get; set;}
+        public bool IsOptional { get; set; }
+
+        public FromAttributeAttribute(string attributeName)
+        {
+            AttributeName = attributeName;
+        }
+
+        public FromAttributeAttribute(string attributeName, bool isOptional)
+        {
+            AttributeName = attributeName;
+            IsOptional = isOptional;
+        }
+    }
+}

src/Blazor.Runtime/Components/RazorComponent.cs

@@ -5,6 +5,7 @@
 using System.Linq;
 using Blazor.Routing;
 using Blazor.Runtime.Components;
+using System.Reflection;
 using Blazor.Runtime.Interop;
 
 namespace Blazor.Components
@@ -56,9 +57,45 @@ protected override void RenderVirtualDom()
             // don't have to be marked abstract.
         }
 
+        private static Dictionary<Type, IEnumerable<MemberInfo>> ParameterMembersCache = new Dictionary<Type, IEnumerable<MemberInfo>>();
+        private IEnumerable<MemberInfo> GetComponentParameterMembers()
+        {
+            if (ParameterMembersCache.ContainsKey(this.GetType()))
+            {
+                return ParameterMembersCache[this.GetType()];
+            }
+
+            var decoratedMembers = new List<MemberInfo>();
+
+
+            decoratedMembers.AddRange(this.GetType().GetTypeInfo().DeclaredFields.Where(x => x.GetCustomAttribute(typeof(FromAttributeAttribute), true) != null));
+            decoratedMembers.AddRange(this.GetType().GetTypeInfo().DeclaredProperties.Where(x => x.GetCustomAttribute(typeof(FromAttributeAttribute),true) != null));
+
+            ParameterMembersCache.Add(this.GetType(), decoratedMembers);
+            return decoratedMembers;
+        }
+
         protected override void ReceiveParameters(IDictionary<string, object> parameters)
         {
-            // Subclasses may optionally override this
+            var decoratedMembers = GetComponentParameterMembers();
+
+            foreach (var member in decoratedMembers)
+            {
+
+                var attribute = (FromAttributeAttribute)member.GetCustomAttributes().First(x => x.GetType() == typeof(FromAttributeAttribute));
+                if (!parameters.ContainsKey(attribute.AttributeName) && !attribute.IsOptional)
+                {
+                    throw new Exception($"Parameter '{attribute.AttributeName}' is required");
+                }
+
+                var parameterValue = parameters[attribute.AttributeName];
+
+
+                if(member is FieldInfo)
+                    ((FieldInfo)member).SetValue(this, parameterValue);
+                else
+                    ((PropertyInfo)member).SetValue(this, parameterValue);
+            }
         }
 
         private static Type GetTypeForCompiledRazorFile(string cshtmlFilename)
@@ -102,7 +139,7 @@ protected VDomAttribute onclick(Action callback)
             };
         }
 
-        protected VDomAttribute onclick(Action<EventInfo> callback)
+        protected VDomAttribute onclick(Action<VirtualDom.EventInfo> callback)
         {
             return new VDomAttribute
             {
@@ -120,7 +157,7 @@ protected VDomAttribute onclickAsync(Func<Task> callback)
             };
         }
 
-        protected VDomAttribute onclickAsync(Func<EventInfo, Task> callback)
+        protected VDomAttribute onclickAsync(Func<VirtualDom.EventInfo, Task> callback)
         {
             return new VDomAttribute
             {
@@ -129,7 +166,7 @@ protected VDomAttribute onclickAsync(Func<EventInfo, Task> callback)
             };
         }
 
-        protected VDomAttribute onchange(Action<EventInfo> callback)
+        protected VDomAttribute onchange(Action<VirtualDom.EventInfo> callback)
         {
             return new VDomAttribute
             {