// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002010/fileinfo-changeextension

​

// @nuget: Z.ExtensionMethods

​

using System;

public class Program

{

    public static void Main()

    {

        string FileName = "test.txt";

        Console.WriteLine("File name: {0}",FileName);

        // C# Extension Method: FileInfo - ChangeExtension

        string newFileName = FileName.ToFileInfo().ChangeExtension("md");

        Console.WriteLine("File name after changing extension: {0}", newFileName);

    }

}