Sample for extending an index from client-side for ravendb 4.0

IndexExtensionFromClient.cs

      public class Checkin_ByDay : AbstractIndexCreationTask<Checkin>
      {
          public class Result
          {
              public string Id { get; set; }
              public int Count { get; set; }
              public string[] Names { get; set; }
          }
          public Checkin_ByDay()
          {
              Map = entities => from entity in entities
                  select new
                  {
                      Count = entity.Count,
                      Day = entity.When.Date,
                      Names = new[] { entity.Name.NamePlusExt("plus") } // using extension methods on the fields
                  }.AppendCommonProperty(); // adding common properties on a resulting object

              StoreAllFields(FieldStorage.Yes);

              AdditionalSources = new Dictionary<string, string>()
              {
                  {"RandomClass", @"
using System;

namespace My.Crazy.Namespace {
  public static class RandomClass {
      public static object AppendCommonProperty(this object test)
      {
          var x = (dynamic)test;
          x.Common = true;
          return x;
      }

      public static string NamePlus(string name, string plus){
          return name + plus;
      }
      public static string NamePlusExt(this string name, string plus){
          return name + plus;
      }
  }
}
"}
              };
          }
      }
        
public class Checkin
{
    public string Id { get; set; }
    public string Name { get; set; }
    public DateTimeOffset When { get; set; }
    public int Count { get; set; }
}