Improve logic for choosing constructor in type deserializator generator.

Now we choose by accessibility level, with importance: public > internal == protected > private and then by number of arguments: giving priority to the argumentless constructor.

Dapper/SqlMapper.cs

@@ -1504,9 +1504,18 @@ static List<FieldInfo> GetSettableFields(Type t)
                     types[i - startBound] = reader.GetFieldType(i);
                 }
                 var constructors = type.GetConstructors(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
-                foreach(ConstructorInfo ctor in constructors)
+                bool hasDefaultConstructor = false;
+                foreach (ConstructorInfo ctor in constructors.OrderBy(c => c.IsPublic ? 0 : (c.IsPrivate ? 2 : 1)).ThenBy(c => c.GetParameters().Length))
                 {
                     ParameterInfo[] ctorParameters = ctor.GetParameters();
+                    if (ctorParameters.Length == 0)
+                    {
+                        il.Emit(OpCodes.Newobj, ctor);
+                        il.Emit(OpCodes.Stloc_1);
+                        hasDefaultConstructor = true;
+                        break;
+                    }
+
                     if (ctorParameters.Length != types.Length)
                         continue;
                     int i = 0;
@@ -1529,15 +1538,9 @@ static List<FieldInfo> GetSettableFields(Type t)
                         break;
                     }
                 }
-                if(specializedConstructor == null)
+                if (!hasDefaultConstructor && specializedConstructor == null)
                 {
-                    var ctor = type.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null);
-                    if (ctor == null)
-                    {
-                        throw new InvalidOperationException("A parameterless default constructor is required to allow for dapper materialization");
-                    }
-                    il.Emit(OpCodes.Newobj, ctor);
-                    il.Emit(OpCodes.Stloc_1);
+                    throw new InvalidOperationException("A parameterless default constructor or one matching order, names and types of values returned by the query is required to allow for dapper materialization");
                 }
             }
             il.BeginExceptionBlock();

Tests/Tests.cs

@@ -33,6 +33,49 @@ public class ConcreteOrder : Order
             }
         }
 
+        class MultipleConstructors
+        {
+            public MultipleConstructors()
+            {
+
+            }
+            public MultipleConstructors(int a, string b)
+            {
+                A = a + 1;
+                B = b + "!";
+            }
+            public int A { get; set; }
+            public string B { get; set; }
+        }
+
+        public void TestMultipleConstructors()
+        {
+            MultipleConstructors mult = connection.Query<MultipleConstructors>("select 0 A, 'Dapper' b").First();
+            mult.A.IsEqualTo(0);
+            mult.B.IsEqualTo("Dapper");
+        }
+
+        class ConstructorsWithAccessModifiers
+        {
+            private ConstructorsWithAccessModifiers()
+            {
+            }
+            public ConstructorsWithAccessModifiers(int a, string b)
+            {
+                A = a + 1;
+                B = b + "!";
+            }
+            public int A { get; set; }
+            public string B { get; set; }
+        }
+
+        public void TestConstructorsWithAccessModifiers()
+        {
+            ConstructorsWithAccessModifiers value = connection.Query<ConstructorsWithAccessModifiers>("select 0 A, 'Dapper' b").First();
+            value.A.IsEqualTo(1);
+            value.B.IsEqualTo("Dapper!");
+        }
+
         class NoDefaultConstructor
         {
             public NoDefaultConstructor(int a1, int? b1, float f1, string s1, Guid G1)