// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002104/string-extractletter

​

// @nuget: Z.ExtensionMethods

​

using System;

using System.IO;

​

public class Program

{   

    public static void Main()

    {   

        string input = "Mwasdf{123c[45z6]6c7v8}";

​

        //C# Extension Method: String - ExtractLetter

        var output = input.ExtractLetter();

​

        Console.WriteLine(output);

    }

}