LINQ expression String.Contains doesn't work - asp.net-mvc

Question

I have a Kendo Grid, which has to be filtered by a column. It works fine with IsEqualTo, IsNotEqualTo, StartsWith and EndsWith cases but not with Contains or DoesNotContain cases.
My code is like:
switch (ertesitettDescriptor.Operator)
{
case FilterOperator.IsEqualTo:
res = res.Where(m => m.ErtesitendoSzerv.Nev.ToLower() == filterValue.ToLower());
break;
case FilterOperator.IsNotEqualTo:
res = res.Where(m => !(m.ErtesitendoSzerv.Nev.ToLower() == filterValue.ToLower()));
break;
case FilterOperator.Contains:
res = res.Where(m => m.ErtesitendoSzerv.Nev.ToLower().Contains(filterValue.ToLower()));
break;
case FilterOperator.DoesNotContain:
res = res.Where(m => !(m.ErtesitendoSzerv.Nev.ToLower().Contains(filterValue.ToLower())));
break;
case FilterOperator.StartsWith:
res = res.Where(m => (m.ErtesitendoSzerv.Nev.ToLower().StartsWith(filterValue.ToLower())));
break;
case FilterOperator.EndsWith:
res = res.Where(m => (m.ErtesitendoSzerv.Nev.ToLower().EndsWith(filterValue.ToLower())));
break;
default:
return new JavaScriptResult { Script = "kendo.alert('A szűrés módja nem támogatott!')" };
}
All works fine, so the values are ok, but the .Contains method doesn't give back any records.

Answer 1

If you are using LINQ to SQL, it automatically ignores case sensitivity. You can achieve results without converting it to lowercase or uppercase.
res = res.Where(m => !(m.ErtesitendoSzerv.Nev.Contains(filterValue)));

Answer 2

Just took the liberty of cleaning up the code alittle, and added StringComparison to your filtering. i assume the StringComparison solves your issue, as you no longer need to use ToLower().
StringComparison comp = StringComparison.OrdinalIgnoreCase;
switch (ertesitettDescriptor.Operator)
{
case FilterOperator.IsEqualTo:
res = res.Where(m => m.ErtesitendoSzerv.Nev.Equals(filterValue, comp);
break;
case FilterOperator.IsNotEqualTo:
res = res.Where(m => !m.ErtesitendoSzerv.Nev.Equals(filterValue, comp);
break;
case FilterOperator.Contains:
res = res.Where(m => m.ErtesitendoSzerv.Nev.Contains(filterValue, comp));
break;
case FilterOperator.DoesNotContain:
res = res.Where(m => !m.ErtesitendoSzerv.Nev.Contains(filterValue, comp));
break;
case FilterOperator.StartsWith:
res = res.Where(m => m.ErtesitendoSzerv.Nev.StartsWith(filterValue, comp));
break;
case FilterOperator.EndsWith:
res = res.Where(m => m.ErtesitendoSzerv.Nev.EndsWith(filterValue, comp));
break;
default:
return new JavaScriptResult { Script = "kendo.alert('A szűrés módja nem támogatott!')" };
}