Search string within a string array in a LINQ expression

Question

if (!string.IsNullOrEmpty(Queries["SurnameInitial"]))
{
    var initials = Queries["SurnameInitial"].Split(',').ToList();
        filter.And(s => initials.Contains(s.Surname.ToArray()[0].ToString()));
}

It throws exception

LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.

How can i match char vs string?

Answer 1

You can use the following s.Surname.First() instead:

if (!string.IsNullOrEmpty(Queries["SurnameInitial"]))
{
    var initials = Queries["SurnameInitial"].Split(',');
        filter.And(s => initials.Contains(s.Surname.First()));
}

This happens because Linq to Entities doesn't know what to do with char.ToString()

Since you're dealing with a List<string> you can use:

filter.And(s => initials.Any(x => x.Contains(s.Surname.First()));

Answer 2

The following code solved my problem-

 var initials = Queries["SurnameInitial"].Split(',').ToList();
 filter.And(s => initials.Contains(s.Surname.Substring(0, 1)));