using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.Json;

public class Program

{

    public static void Main()

    {

        var ColumnsSwapped = new List<FromTextFile>

        {

            new FromTextFile { Column1 = "QA7878729D", Column2 = "D9278787AQ" },

            new FromTextFile { Column1 = "QA7878736A", Column2 = "A6378787AQ" },

            new FromTextFile { Column1 = "QA7878751B", Column2 = "B1578787AQ" },

            new FromTextFile { Column1 = "QA7878834C", Column2 = "C4388787AQ" },

            new FromTextFile { Column1 = "QB7878726D", Column2 = "D6278787BQ" },

        };

        List<FromTextFile> SortedList = ColumnsSwapped

            .OrderBy(o => o.Column1.Substring(0, 2))

            .ThenBy(o => o.Column2.Substring(0, 1))

            .ThenBy(o => o.Column1)

            .ThenBy(o => o.Column2)

            .ToList();

        FiddleHelper.WriteTable(SortedList);

    }

}

​

public class FromTextFile

{

    public string Column1{ get; set; }

    public string Column2{ get; set; }

}