don't init outputCallbacks unless there are callbacks

Dapper NET40/SqlMapper.cs

@@ -4277,14 +4277,20 @@ protected void AddParameters(IDbCommand command, SqlMapper.Identity identity)
                 }
 
                 // Now that the parameters are added to the command, let's place our output callbacks
-                foreach (var generator in this.outputCallbacks)
+                var tmp = outputCallbacks;
+                if (tmp != null)
+                {
+                    foreach (var generator in tmp)
                     {
                         generator();
                     }
                 }
+            }
 
-            foreach (var param in parameters.Values.Where(p => !p.CameFromTemplate))
+            foreach (var param in parameters.Values)
             {
+                if (param.CameFromTemplate) continue;
+
                 var dbType = param.DbType;
                 var val = param.Value;
                 string name = Clean(param.Name);
@@ -4525,7 +4531,7 @@ public DynamicParameters Output<T>(T target, Expression<Func<T, object>> express
 
             // Queue the preparation to be fired off when adding parameters to the DbCommand
             MAKECALLBACK:
-            this.outputCallbacks.Add(() =>
+            (outputCallbacks ?? (outputCallbacks = new List<Action>())).Add(() =>
             {
                 // Finally, prep the parameter and attach the callback to it
                 ParamInfo parameter;
@@ -4559,7 +4565,7 @@ public DynamicParameters Output<T>(T target, Expression<Func<T, object>> express
             return this;
         }
 
-        private readonly List<Action> outputCallbacks = new List<Action>();
+        private List<Action> outputCallbacks;
 
         private readonly Dictionary<string, Action<object, DynamicParameters>> cachedOutputSetters = new Dictionary<string,Action<object,DynamicParameters>>();
 

Tests/Tests.cs

@@ -1176,7 +1176,6 @@ public void TestSupportForDynamicParameters()
             p.Get<int>("age").IsEqualTo(11);
         }
 
-        [ActiveTest]
         public void TestSupportForDynamicParametersOutputExpressions()
         {
             var bob = new Person { Name = "bob", PersonId = 1, Address = new Address { PersonId = 2 } };