How to find the parent list using Linq Query for below

Question

I Have classes public class User { Int UserId; String UserName products List } public class Product { int ProductId; int ProductName; } var data = new List (); data.Add(1, new List { new Product {prdouctId= 1, ProductName = "Name1"} , new Product {ProductId=2, ProductName="Name2"}} data.Add(2, new List { new Product {prdouctId= 2, ProductName = "Name2"} , new Product {ProductId=3, ProductName="Name3"}} data.Add(3, new List { new Product {prdouctId= 4, ProductName = "Name4"} , new Product {ProductId=2, ProductName="Name1"}} How we get the users List with Linq query who are mapped product wise Expected Result: ---------------------- ProdcutId UsersId 1 {1,3} 2 {1,2,3} 3 {2,3}

Hemant Jindal · Answer

Hi Rakesh I have changed the implementation a bit. Please have a look and hope this works for you static List InitializeUserProduct() { List Users = new List (); List Products = new List (); Products.Add( new Product() { ProductId = 1, ProductName = "Product 1" }); Products.Add( new Product() { ProductId = 2, ProductName = "Product 2" }); Products.Add( new Product() { ProductId = 3, ProductName = "Product 3" }); Products.Add( new Product() { ProductId = 4, ProductName = "Product 4" }); User user = new User() {UserId = 1, UserName = "User 1" }; user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 1)); user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 2)); Users.Add(user); user = new User() { UserId = 2, UserName = "User 2" }; user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 2)); user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 3)); Users.Add(user); user = new User() { UserId = 3, UserName = "User 3" }; user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 1)); user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 2)); user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 3)); user.Products.Add(Products.FirstOrDefault(p => p.ProductId == 4)); Users.Add(user); Products.ForEach(product => { var users = Users.Where(u => u.Products.Exists(p => p.ProductId == product.ProductId)).Select(u => new User() { UserId = u.UserId, UserName = u.UserName }); string associatedUsers = string .Join( ", " , from item in users.AsEnumerable() select item.UserName); Console.WriteLine( "Product Id: {0}, Product Name : {1} Users: {2} " , product.ProductId, product.ProductName, associatedUsers); }); return Users; } Please let me know if you have any queries Thanks Hemant Jindal

Rakesh reddy · Answer

Hi Hemant, Thank you for response, But while finding users based on Product wise you are hardcoded product==1, But in my scenariao i should not data is dynamic and with single Linq query i have to get the belwo result Expected Result: ---------------------- ProdcutId UsersId 1 {1,3} 2 {1,2,3} 3 {2,3} finally i need to get the only 3 records with List property for each row

Hemant Jindal · Answer

i Rakesh I hope sample code help you public class User { public int UserId { get ; set ; } public string UserName { get ; set ; } private List _products; public List Products { get { return _products ?? (_products = new List ()); } set { _products = value; } } } public class Product { public int ProductId { get ; set ; } public string ProductName { get ; set ; } } static List InitializeUserProduct() { List Users = new List (); User user = new User() {UserId = 1, UserName = "User 1" }; user.Products.Add( new Product() {ProductId = 1, ProductName = "Product 1" }); user.Products.Add( new Product() {ProductId = 2, ProductName = "Product 2" }); Users.Add(user); user = new User() { UserId = 2, UserName = "User 2" }; user.Products.Add( new Product() { ProductId = 2, ProductName = "Product 2" }); user.Products.Add( new Product() { ProductId = 3, ProductName = "Product 3" }); Users.Add(user); user = new User() { UserId = 3, UserName = "User 3" }; user.Products.Add( new Product() { ProductId = 1, ProductName = "Product 1" }); user.Products.Add( new Product() { ProductId = 3, ProductName = "Product 3" }); user.Products.Add( new Product() { ProductId = 4, ProductName = "Product 4" }); Users.Add(user); var users = Users.Where(u => u.Products.Exists(p => p.ProductId == 1)).Select(u => new User(){ UserId = u.UserId, UserName = u.UserName}); return Users; } ic void Main( string [] args) { InitializeUserProduct(); Console.ReadLine(); } thanks Hemant Jindal