diff --git a/Scripts/Node.cs b/Scripts/Node.cs
index beb5f77..30709cf 100644
--- a/Scripts/Node.cs
+++ b/Scripts/Node.cs
@@ -378,7 +378,13 @@ namespace XNode {
                 this.Clear();
 
                 if (keys.Count != values.Count)
-                    throw new System.Exception("there are " + keys.Count + " keys and " + values.Count + " values after deserialization. Make sure that both key and value types are serializable.");
+                {
+                    var msg = string.Format(
+                        XNodeRuntimeConstants.MISMATCHED_KEYS_TO_VALUES_EXCEPTION_MESSAGE,
+                        keys.Count,
+                        values.Count);
+                    throw new Exception(msg);
+                }
 
                 for (int i = 0; i < keys.Count; i++)
                     this.Add(keys[i], values[i]);
diff --git a/Scripts/NodeDataCache.cs b/Scripts/NodeDataCache.cs
index ad55f7b..e1a6c4d 100644
--- a/Scripts/NodeDataCache.cs
+++ b/Scripts/NodeDataCache.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
 using UnityEngine;
@@ -121,27 +122,20 @@ namespace XNode {
         /// <summary> Cache node types </summary>
         private static void BuildCache() {
             portDataCache = new PortDataCache();
-            System.Type baseType = typeof(Node);
-            List<System.Type> nodeTypes = new List<System.Type>();
-            System.Reflection.Assembly[] assemblies = System.AppDomain.CurrentDomain.GetAssemblies();
+            Type baseType = typeof(Node);
+            List<Type> nodeTypes = new List<Type>();
+            Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
 
             // Loop through assemblies and add node types to list
-            foreach (Assembly assembly in assemblies) {
+            foreach (Assembly assembly in assemblies)
+            {
                 // Skip certain dlls to improve performance
                 string assemblyName = assembly.GetName().Name;
-                int index = assemblyName.IndexOf('.');
-                if (index != -1) assemblyName = assemblyName.Substring(0, index);
-                switch (assemblyName) {
-                    // The following assemblies, and sub-assemblies (eg. UnityEngine.UI) are skipped
-                    case "UnityEditor":
-                    case "UnityEngine":
-                    case "System":
-                    case "mscorlib":
-                    case "Microsoft":
-                        continue;
-                    default:
-                        nodeTypes.AddRange(assembly.GetTypes().Where(t => !t.IsAbstract && baseType.IsAssignableFrom(t)).ToArray());
-                        break;
+                if (!XNodeRuntimeConstants.IGNORE_ASSEMBLY_PREFIXES.Any(x => assemblyName.StartsWith(x)))
+                {
+                    IEnumerable<Type> foundNodeTypes = assembly.GetTypes()
+                        .Where(t => !t.IsAbstract && baseType.IsAssignableFrom(t));
+                    nodeTypes.AddRange(foundNodeTypes);
                 }
             }
 
@@ -201,7 +195,13 @@ namespace XNode {
                 this.Clear();
 
                 if (keys.Count != values.Count)
-                    throw new System.Exception(string.Format("there are {0} keys and {1} values after deserialization. Make sure that both key and value types are serializable."));
+                {
+                    var msg = string.Format(
+                        XNodeRuntimeConstants.MISMATCHED_KEYS_TO_VALUES_EXCEPTION_MESSAGE,
+                        keys.Count,
+                        values.Count);
+                    throw new Exception(msg);
+                }
 
                 for (int i = 0; i < keys.Count; i++)
                     this.Add(keys[i], values[i]);
diff --git a/Scripts/XNodeRuntimeConstants.cs b/Scripts/XNodeRuntimeConstants.cs
new file mode 100644
index 0000000..027f979
--- /dev/null
+++ b/Scripts/XNodeRuntimeConstants.cs
@@ -0,0 +1,33 @@
+namespace XNode
+{
+    /// <summary>
+    /// A helper class containing shared constants.
+    /// </summary>
+	public static class XNodeRuntimeConstants
+	{
+        // Exceptions
+		public const string MISMATCHED_KEYS_TO_VALUES_EXCEPTION_MESSAGE =
+			"There are {0} keys and {1} values after deserialization. " +
+			"Make sure that both key and value types are serializable.";
+
+        // Reflection
+
+        /// <summary>
+        /// A collection of assembly prefixes that should not be reflected for derived node types.
+        /// </summary>
+        public static string[] IGNORE_ASSEMBLY_PREFIXES =
+        {
+            "ExCSS",
+            "Microsoft",
+            "Mono",
+            "netstandard",
+            "mscorlib",
+            "nunit",
+            "SyntaxTree",
+            "System",
+            "Unity",
+            "UnityEditor",
+            "UnityEngine"
+        };
+	}
+}
diff --git a/Scripts/XNodeRuntimeConstants.cs.meta b/Scripts/XNodeRuntimeConstants.cs.meta
new file mode 100644
index 0000000..c4040a8
--- /dev/null
+++ b/Scripts/XNodeRuntimeConstants.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: cf01fc218f8f12d4aa557c9799289063
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: