EF Core Join Discover How to Combine Row of Many Entities in LINQ
Introduction
In SQL, a JOIN clause is used to combine rows from two or more tables, based on a related column between them. In Entity Framework Core you can use the Join() and GroupJoin() method to achieve the same results.
The following query joins Customers and Invoices table using the Join() method.
var query = context.Customers .Join( context.Invoices, customer => customer.CustomerId, invoice => invoice.Customer.CustomerId, (customer, invoice) => new { InvoiceID = invoice.Id, CustomerName = customer.FirstName + "" + customer.LastName, InvoiceDate = invoice.Date } ).ToList(); foreach (var invoice in query) { Console.WriteLine("InvoiceID: {0}, Customer Name: {1} " + "Date: {2} ", invoice.InvoiceID, invoice.CustomerName, invoice.InvoiceDate); }
The following example performs a GroupJoin over the Invoices and InvoiceItems tables to find all items per invoice.
var query = context.Invoices .GroupJoin( context.InvoiceItems, invoice => invoice, item => item.Invoice, (invoice, invoiceItems) => new { InvoiceId = invoice.Id, Items = invoiceItems.Select(item => item.Code) } ).ToList(); foreach (var obj in query) { Console.WriteLine("{0}:", obj.InvoiceId); foreach (var item in obj.Items) { Console.WriteLine(" {0}", item); } }
Author: ZZZ Projects