LINQ To Entity Framework Tutorial – Part II

In this post, I am going to explain below operations in LINQ.
  1. Sorting
  2. Group By
  3. Left Join
1) Sorting: Ascending:
Employee[] AllEmployees = (from E in NorthwindEntity.Employees
orderby E.FirstName ascending
select E).ToArray();

Descending:
Employee[] AllEmployees = (from E in NorthwindEntity.Employees
orderby E.FirstName descending
select E).ToArray();

2) Group By: 
    var AllEmployee = from E in NorthwindEntity.Employees
group E by E.LastName into G
select new { LastName = G.Key, Group = G };

foreach (var employees in AllEmployee)
{
// employees.Group is the current group 
// Here you will find each group ( using employees.Group ) for employees.LastName

foreach (var employee in employees.Group)
{
// Here you will find each employee in particular group
// You can access each property of Employee object here.
}
}
3) Left Join:
    var allProductsWithCategory = from p in NorthwindEntity.Products
let c = (from c in NorthwindEntity.Categories
where c.CategoryID == p.CategoryID
select c).FirstOrDefault()
select new { Productname = p.ProductName, CategoryName = c.CategoryName };

foreach (var item in allProductsWithCategory)
{

// You will find product's name and category row by row here...
// item.Productname
// item.CategoryName;

}
That’s all for today’s post, In my next post I will try to upload demo project to understand LINQ more.
For next post I have two topics in my mind:
  1. Using lambda expressions
  2. Bulk insert / update / delete operations

Comments

Post a Comment

Popular posts from this blog

Lambda Expressions In Entity Framework

From the two options I mentioned in my last post, I chose lambda expression for this post for those programmers who are not much comfortable with SQL like LINQ query. Microsoft gives us very good option called “Lambda Expression”. In this post I am going to demonstrate below operations: Simple select query using LINQ & Simple select query using lambda expression Select query with where condition using LINQ & select query with where condition using lambda expression Inner Join using LINQ & Inner Join using lambda expression Left Join using LINQ & Left Join using lambda expression Group by using LINQ & Group by using lambda expression Sorting using LINQ & Sorting using lambda expression Simple select: // Using LINQ Employee [] allEmployees1 = ( from E in NorthwindEntity.Employees select E).ToArray(); // Using lambda expression Employee [] allEmployees2 = NorthwindEntity.Employees.ToArray(); // Where condition using LINQ Employee [] allEmployees1 = ( from ...
Read more

Select Columns From Multiple Tables Using LINQ

From Northwind database, to show all available products it needs to select values from multiple tables because in Products table there are two columns – CategoryID and SupplierID which are referenced from Category and Suppliers tables. There are more then one options to do this but I use below way to select from multiple tables and bind to grid. First of all create a class and create properties, ProductID, ProductName, CompanyName, CategoryName, UnitPrice. These are the properties which I want to show in grid. public class AvailableProducts { public int ProductID { get ; set ; } public string ProductName { get ; set ; } public string CompanyName { get ; set ; } public string CategoryName { get ; set ; } public decimal UnitPrice { get ; set ; } } Now, write below function in data access layer: public List < AvailableProducts > GetAllAvailableProducts() { var linqAllProducts = from p in NorthwindEntity.Products from c in NorthwindEntity.Categories from s in NorthwindEntity.Supp...
Read more

LINQ To Entity Framework Tutorial

As a startup, I choose this topic for those beginners who wants to use Entity Framework. The ADO.NET Entity Framework helps developers to access database very easily. All you need is to create a data model from actual database and programming against generated data model instead of programming directly against the actual database by either creating stored procedure or writing select/insert/update/delete query in data access layer itself. Using this way of programming during the development phase of the project helps to reduce amount of code to access database and also reduce maintenance work in future. Please follow below steps in order to create data access application using ADO.NET Entity Framework. In this tutorial I am using “Northwind” database in backend. Create new “ASP.Net Empty Web Application” using Visual Studio 2010. Create new folder under web application project. Name it “DataAccess” Right click on “DataAccess” folder and click on Add –> New Item… Select “Dat...
Read more