using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        const string input = @"ABCD+=abc@#~AB";

        const string pattern = "[^A-Za-z~_-]";

​

        var regex = new Regex(pattern);

        string sanitized = regex.Replace(input, " ");

        Console.WriteLine(sanitized);

    }

}