using static System.Console;
using System.Text;
 
public class Program {
    public static void Main() {
        WriteLine("Digite uma frase: ");
        var frase = ReadLine();
        WriteLine($"Original string: {frase}");
        var invertida = new StringBuilder(frase.Length);
        foreach (var chr in frase) invertida.Append(char.ToLower(chr == ' ' ? '0' : chr));
        WriteLine($"Character array: {invertida}");
    }
}
 
//https://pt.stackoverflow.com/q/325081/101

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

dGVzdGUgZGUgZnJhc2UK

teste de frase