Find consecutive numbers in a string in C #

You can do this with a character scan and a single loop, like this (Example in dotnetfiddle) :

string input = "Abc111de2234";
string output = string.Empty; // Desejado: "Abc1de234";
char[] numbers = new []{ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

if(!string.IsNullOrWhiteSpace(input))
    for(int i = 0; i < input.Length; i++)
        if (i > 0)
        {
            if (numbers.Contains(input[i]))
            {
                if(input[i] != input[i-1])
                    output += input[i];
            }
            else
                output += input[i];
        }
        else
            output += input[i];

Console.WriteLine(output);

Other ways to do this include using regular expressions, for example, but I believe this would be less performative.

I would do so:

using static System.Console;

public class Program {
    public static void Main() {
        var texto = "Abcc111de12234";
        var lista = new char[texto.Length];
        for (int i = 0, j = 0; i < texto.Length; i++) if (!char.IsDigit(texto[i]) || (i == 0 || texto[i] != texto[i - 1])) lista[j++] = texto[i];
        WriteLine(new string(lista));
    }
}

See running on .NET Fiddle . And no Coding Ground . Also I placed GitHub for future reference .

The other answer's solution generates several string allocations and copies , making to slow application and consuming lots of memory , as well as causing pauses. There are other inefficiencies.