using System;

using System.Linq;

using System.Globalization;

using System.Text;

using System.Collections.Generic;

​

public class Program

{

    public static bool HasDiacritics(string value)

    {

        if (value == null)

            return false;

        var normalize = value.Normalize(NormalizationForm.FormD);

        var sb = new StringBuilder();

        foreach (var t in normalize.Where(t => CharUnicodeInfo.GetUnicodeCategory(t) != UnicodeCategory.NonSpacingMark))

            sb.Append(t);

        return (sb.ToString().Normalize(NormalizationForm.FormC) != value);

    }

​

    public static void Main(string[] args)

    {

        var list = new List<string>()

        {"Lina want to go to school. Mi rư xă", "Lina want to go to school", "Lina want to go to sch`ool", "Lina want Ξ, ©, ±", };

        var results = list.Select(HasDiacritics);

        foreach (var result in results)

            Console.WriteLine(result);

    }

}