using static System.Console;

using static System.Math;

using static System.Convert;

using static System.Globalization.NumberStyles;

using System.Globalization;

​

var x = 1.41293;

WriteLine(x.ToString("N3"));

WriteLine(Round(x, 3));

WriteLine(Round(ToDecimal(x), 3));

if (!decimal.TryParse("1,41293", Number, new CultureInfo("pt-BR"), out var numero)) return;

WriteLine(Round(numero, 3));