Add Check

Src/Asp.Net/SqlSugar/Abstract/QueryableProvider/QueryableProvider.cs

@@ -115,6 +115,7 @@ namespace SqlSugar
         }
         public ISugarQueryable<T> Mapper<TObject>(Expression<Func<T, TObject>> mapperObject, Expression<Func<T, object>> mainField, Expression<Func<T, object>> childField)
         {
+            Check.Exception(mapperObject.ReturnType.Name == "IList`1", "Mapper no support IList , Use List<T>");
             return _Mapper<TObject>(mapperObject, mainField, childField);
         }
         public ISugarQueryable<T> Mapper<TObject>(Expression<Func<T, List<TObject>>> mapperObject, Expression<Func<T, object>> mainField, Expression<Func<T, object>> childField)