leftjoin-lambda

CSharp · Console

/Program.cs

using System;
using System.Linq;
using System.Collections.Generic;

					
public class Program
{
	public static void Main()
	{
		            List<Group> _groups = new List<Group>();
            List<CategoryRoot> _categoryRoots = new List<CategoryRoot>();
            List<Category> _categories = new List<Category>();

            _categories.Add(new Category { Id = 1, Name = "C 1", CategoryRoot_Id = 1 });
            _categories.Add(new Category { Id = 2, Name = "C 2", CategoryRoot_Id = 1 });
            _categories.Add(new Category { Id = 3, Name = "C 3", CategoryRoot_Id = 3 });

            _categoryRoots.Add(new CategoryRoot { Id = 1, Name = "CR 1", Group_Id = 1, Categories = _categories.Where(p => p.CategoryRoot_Id == 1).ToList() });
            _categoryRoots.Add(new CategoryRoot { Id = 2, Name = "CR 2", Group_Id = 1, Categories = _categories.Where(p => p.CategoryRoot_Id == 2).ToList() });
            _categoryRoots.Add(new CategoryRoot { Id = 3, Name = "CR 3", Group_Id = 2, Categories = _categories.Where(p => p.CategoryRoot_Id == 3).ToList() });
            _categoryRoots.Add(new CategoryRoot { Id = 4, Name = "CR 4", Group_Id = 3, Categories = _categories.Where(p => p.CategoryRoot_Id == 4).ToList() });

            _groups.Add(new Group { Id = 1, Name = "Group A", CategoryRoots = _categoryRoots.Where(p => p.Group_Id == 1).ToList() });
            _groups.Add(new Group { Id = 2, Name = "Group B", CategoryRoots = _categoryRoots.Where(p => p.Group_Id == 2).ToList() });
            _groups.Add(new Group { Id = 3, Name = "Group C", CategoryRoots = _categoryRoots.Where(p => p.Group_Id == 3).ToList() });
            _groups.Add(new Group { Id = 4, Name = "Group D", CategoryRoots = _categoryRoots.Where(p => p.Group_Id == 4).ToList() });


            var results = (from g in _groups
                         join cr in _categoryRoots on g.Id equals cr.Group_Id into gcr
                         from lgc in gcr.DefaultIfEmpty(new CategoryRoot())
                         join c in _categories on lgc.Id equals c.CategoryRoot_Id into ccr
                         from lccr in ccr.DefaultIfEmpty()
                         select new GroupCategory
                         {
                             Id = g.Id,
                             Name = g.Name,
                             CategoryRoot_Id = lgc == null ? 0: lgc.Id,
                             CategoryRootName = lgc == null ? "": lgc.Name,
                             Category_Id = lccr == null ? 0: lccr.Id,
                             CategoryName = lccr == null ? "": lccr.Name
                         }).ToList();
		
		
		    foreach (var result in results)
            {
                //Console.WriteLine("Id:{0} Name:{1} CategoryRoot_Id:{2} CateoryName:{3} Category_Id:{4} CategoryName:{5}", result.Id, result.Name, result.CategoryRoot_Id, result.CategoryRootName, result.Category_Id, result.CategoryName);

                Console.WriteLine("Id:{0} Name:{1} CR:{2} CRN:{3} C:{4} CName:{5}", result.Id, result.Name, result.CategoryRoot_Id, result.CategoryRootName, result.Category_Id, result.CategoryName);
                
            }
		Console.WriteLine("------------------------");
	}
	
	public class GroupCategory
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int CategoryRoot_Id { get; set; }
        public string CategoryRootName { get; set; }
        public int Category_Id { get; set; }
        public string CategoryName { get; set; }

    }

    public class Group
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public IEnumerable<CategoryRoot> CategoryRoots { get; set; }
    }
    public class CategoryRoot
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Group_Id { get; set; }
        public Group Group { get; set; }
        public IEnumerable<Category> Categories { get; set; }

    }
    public class Category
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int CategoryRoot_Id { get; set; }
        public CategoryRoot CategoryRoot { get; set; }
    }
}