Making SinglePredicateExpressionArgumentType caching thread safe

Author: Tyler Carlson

src/AutoMapper.Collection/AutoMapper.Collection/Equivilency Expression/ExpressionExtentions.cs

@@ -1,13 +1,13 @@
 using System;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Linq;
 using System.Linq.Expressions;
 
 namespace AutoMapper.EquivilencyExpression
 {
     public static class ExpressionExtentions
     {
-        private static readonly IDictionary<Type, Type> _singleParameterTypeDictionary = new Dictionary<Type, Type>();
+        private static readonly ConcurrentDictionary<Type, Type> _singleParameterTypeDictionary = new ConcurrentDictionary<Type, Type>();
 
         public static Type GetSinglePredicateExpressionArgumentType(this Type type)
         {
@@ -33,7 +33,7 @@ public static Type GetSinglePredicateExpressionArgumentType(this Type type)
 
         private static Type CacheAndReturnType(Type type, Type objType)
         {
-            _singleParameterTypeDictionary.Add(type, objType);
+            _singleParameterTypeDictionary.AddOrUpdate(type, objType, (t,t2) => objType);
             return objType;
         }
     }

src/AutoMapper.Collection/AutoMapper.Collection/Properties/AssemblyInfo.cs

@@ -32,5 +32,5 @@
 // You can specify all the values or you can default the Build and Revision Numbers 
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.2.0.0")]
-[assembly: AssemblyFileVersion("1.2.0.0")]
+[assembly: AssemblyVersion("1.2.1.0")]
+[assembly: AssemblyFileVersion("1.2.1.0")]