Add read only property support

Giver.Tests/ComplexTests.cs

@@ -42,6 +42,14 @@ public void With_Many() {
 
             Assert.Equal(testModels.Count, 5);
         }
+
+        [Fact]
+        public void ReadOnly_Property()
+        {
+            OrderLine orderLine = _give.Me<OrderLine>();
+
+            Assert.Equal(orderLine.Price * orderLine.Quantity, orderLine.TotalPrice);
+        }
     }
 
     public class CustomStringGenerator: StringGenerator {

Giver.Tests/Model/OrderLine.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Giver.Tests.Model
+{
+    public class OrderLine
+    {
+        public int Id { get; set; }
+        public decimal Price { get; set; }
+        public int Quantity { get; set; }
+        public decimal TotalPrice => Price * Quantity;
+    }
+}

Giver/Helper.cs

@@ -14,7 +14,7 @@ public static List<Member> GetPrimitiveMembers<T>() {
 #else
             return type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
 #endif
-                .Where(p => IsPrimitive(p.PropertyType))
+                .Where(p => IsPrimitive(p.PropertyType) && p.HasSetter())
                 .Select(p => new Member(p, p.PropertyType))
 #if NET_40
                 .Union(type.GetFields()
@@ -34,6 +34,15 @@ public static bool IsPrimitive(Type type) {
 #endif
         }
 
+        public static bool HasSetter(this PropertyInfo propertyInfo)
+        {
+#if NET_40
+            return propertyInfo.GetSetMethod() != null;
+#else
+            return propertyInfo.SetMethod != null;
+#endif
+        }
+
         public static void SetValue(object instance, MemberInfo memberInfo, object value) {
             var propertyInfo = memberInfo as PropertyInfo;
             if (propertyInfo != null) {