Password verification for special characters

The main condition is that the password was at least one digit, letter, and special symbol. I do not know how you can check this:

Random random = new Random(); List<string> letters = new List<string> {"a","b","c","d","e","f","g","h","i","j","k", "l","m","n","o","p","q","r","s","t","u","v", "w","x","y","z","A","B","C","D","e","f", "G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"}; List<int> numbers = new List<int> {0,1,2,3,4,5,6,7,8,9}; List<string> specialSymbols = new List<string> {"!","@","#","№","$","%","^","&","*","-","_", "?","<",">"}; List<string> newNumbers = numbers.Select(x => x.ToString()).ToList(); var summaryList = letters.Concat(newNumbers).Concat(specialSymbols); IEnumerable<string> list = summaryList.OrderBy(x => random.Next()).Take(10); Console.Write("List<string> with letters: "); foreach (var element in letters) { Console.Write(element); } Console.Write("List<int> with numbers converted to string: "); foreach (var element in newNumbers) { Console.Write(element); } Console.WriteLine(); Console.Write("List<string> with special symbols: "); foreach (var element in specialSymbols) { Console.Write(element); } Console.WriteLine(); string password = ""; Console.Write("Summary List<string> which contains 15 random characters for generating new password: "); foreach (var element in list) { password += element; } Console.Write(password); Console.ReadKey(); 

I ask you to give an answer easier, preferably, since I am still green in this matter. Thank)