main.cs

using System;
using System.IO;

string result;

using (MemoryStream ms = new MemoryStream())
{
    TextWriter tmp = Console.Out;
    using (StreamWriter sw = new StreamWriter(ms))
    {
        Console.SetOut(sw);

        for (int i=0;i<10;i++)
        {
          Console.WriteLine("1=" + i.ToString());
        }

        sw.Close();
        Console.SetOut(tmp);

        result = System.Text.Encoding.UTF8.GetString(ms.ToArray());
    }
}