allow null arrays on suitable RDBMS

Dapper NET40/SqlMapper.cs

@@ -2394,20 +2394,17 @@ public static void PackListParameters(IDbCommand command, string namePrefix, obj
             // initially we tried TVP, however it performs quite poorly.
             // keep in mind SQL support up to 2000 params easily in sp_executesql, needing more is rare
 
-            var list = value as IEnumerable;
-            var count = 0;
-
-            if (list != null)
-            {
             if (FeatureSupport.Get(command.Connection).Arrays)
             {
                 var arrayParm = command.CreateParameter();
-                    arrayParm.Value = list;
+                arrayParm.Value = value ?? DBNull.Value;
                 arrayParm.ParameterName = namePrefix;
                 command.Parameters.Add(arrayParm);
             }
             else
             {
+                var list = value as IEnumerable;
+                var count = 0;
                 bool isString = value is IEnumerable<string>;
                 bool isDbString = value is IEnumerable<DbString>;
                 foreach (var item in list)
@@ -2485,7 +2482,6 @@ public static void PackListParameters(IDbCommand command, string namePrefix, obj
                     });
                 }
             }
-            }
 
         }