পার্ট 8 - Using stored procedures with the entity framework code first approach
পার্ট 9 - Overriding stored procedure defaults with the entity framework code first approach
পার্ট 10 - Entity splitting in entity framework (DB_First Approach)
যখন দুই বা ততোধিক Database টেবিলের মধ্যে একটা common key শেয়ার হয় তখন, Entity Framework এর Entity splitting এই feature টি একটা entity কে সেই দুই বা ততোধিক Database টেবিলের সাথে mapping করে দেয়। আগের পর্বে আমরা Entity Framework এর Entity splitting feature টা database first approach এ আলোচনা করেছিলাম, এই আর্টিকেলে আমরা Entity splitting feature কে code first approach এ আলোচনা করবো।
N.B: Practical ধাপগুলো আমি আপনাদের বোঝার সুবিধার জন্য English এ explain করবো। এই step গুলো VS2017(Visual Studio 2017) এ execute করা হয়েছে।
Step 1: Create a new empty asp.net web application project. Name it Demo. Install entity framework if it's not already installed.
Step 2: Add a class file to the project. Name it Employee.cs. Copy and paste the following code.
namespace Demo
{
public class Employee
{
// These property values should be stored in Employees Table
public int EmployeeId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Gender { get; set; }
// These property values should be stored in EmployeeContactDetails Table
public string Email { get; set; }
public string Mobile { get; set; }
public string Landline { get; set; }
}
}
Step 3: Add a class file to the project. Name it EmployeeDBContext.cs. Copy and paste the following code.
using System.Data.Entity;
namespace Demo
{
public class EmployeeDBContext : DbContext
{
public DbSet<Employee> Employees { get; set; }
}
}
using System.Collections.Generic;
using System.Linq;
namespace Demo
{
public class EmployeeRepository
{
EmployeeDBContext employeeDBContext = new EmployeeDBContext();
public List<Employee> GetEmployees()
{
return employeeDBContext.Employees.ToList();
}
public void InsertEmployee(Employee employee)
{
employeeDBContext.Employees.Add(employee);
employeeDBContext.SaveChanges();
}
public void UpdateEmployee(Employee employee)
{
Employee employeeToUpdate = employeeDBContext.Employees
.SingleOrDefault(x => x.EmployeeId == employee.EmployeeId);
employeeToUpdate.EmployeeId = employee.EmployeeId;
employeeToUpdate.FirstName = employee.FirstName;
employeeToUpdate.LastName = employee.LastName;
employeeToUpdate.Gender = employee.Gender;
employeeToUpdate.Email = employee.Email;
employeeToUpdate.Mobile = employee.Mobile;
employeeToUpdate.Landline = employee.Landline;
employeeDBContext.SaveChanges();
}
public void DeleteEmployee(Employee employee)
{
Employee employeeToDelete = employeeDBContext.Employees
.SingleOrDefault(x => x.EmployeeId == employee.EmployeeId);
employeeDBContext.Employees.Remove(employeeToDelete);
employeeDBContext.SaveChanges();
}
}
}
Step 5: Add the database connection string in web.config file.
<connectionStrings>
<add name="EmployeeDBContext"
connectionString="server=.; database=Sample; integrated security=SSPI;"
providerName="System.Data.SqlClient" />
</connectionStrings>
Step 6: Add a webform to the project. Drag and drop the following 3 controls and build the solution.
1. GridView
2. DetailsView
3. ObjectDataSource
Step 7: Configure ObjectDataSource control
a) Right click on ObjectDataSource control and select "Show Smart Tag" option
b) Click on Configure Data Source link
c) Select Demo.EmployeeRepository on Choose a Business Object screen and click Next
d) On Define Data Methods screen
i) On SELECT tab - Select GetEmployees() method
ii) On UPDATE tab - Select UpdateEmployee(Employee employee) method
iii) On INSERT tab - Select InsertEmployee(Employee employee) method
iv) On DELETE tab - Select DeletEmployee(Employee employee) method
Step 8: Configure GridView control
a) Right click on GridView control and select "Show Smart Tag" option
b) Click on "Auto Format" link and select "Colourful" scheme
c) Select "ObjectDataSource1" from "Choose Data Source" drop-down list
d) Select Enable Editing and Enable Deleting checkboxes
e) Set DataKeyNames="EmployeeId". Do this in the properties window of the GridView control
f) Set ReadOnly="true" for the EmployeeId BoundField. You can do this directly in the HTML Source.
Step 9: Configure DetailsView control
a) Right click on DetailsView control and select "Show Smart Tag" option
b) Click on "Auto Format" link and select "Colourful" scheme
c) Select "ObjectDataSource1" from "Choose Data Source" drop-down list
d) Select Enable Inserting checkbox
e) Set DeafultMode=Insert. Use properties window to set this.
f) Set InsertVisible="false" for the EmployeeId BoundField. You can do this directly in the HTML Source.
g) Generate ItemInserted event handler method for DetailsView control. Copy and paste the following code.
protected void DetailsView1_ItemInserted(object sender, DetailsViewInsertedEventArgse)
{
GridView1.DataBind();
}
Step 10: If you already have Sample database in SQL Server. Delete it from SQL Server Management Studio.
Step 11: Run the application by pressing CTRL + F5. By default, entity framework creates one Table i.e Employees table. But we want entity framework to create the following 2 tables.
a) Employees table with columns EmployeeId, FirstName, LastName, and Gender
b) EmployeeContactDetails table with columns EmployeeId, Email, Mobile and Landline
Step 12: Override OnModelCreating() method to tell entity framework to generate 2 tables(Employees & EmployeeContactDetails) for the Employee entity. OnModelCreating() method is a virtual method present in DbContext class. So, modify EmployeeDBContext class in EmployeeDBContext.cs file as shown below.
public class EmployeeDBContext : DbContext
{
public DbSet<Employee> Employees { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Employee>()
// Specify properties to map to Employees table
.Map(map =>
{
map.Properties(p => new
{
p.EmployeeId,
p.FirstName,
p.LastName,
p.Gender
});
map.ToTable("Employees");
})
// Specify properties to map to EmployeeContactDetails table
.Map(map =>
{
map.Properties(p => new
{
p.EmployeeId,
p.Email,
p.Mobile,
p.Landline
});
map.ToTable("EmployeeContactDetails");
});
base.OnModelCreating(modelBuilder);
}
}
Step 13: Delete the Sample database and run the web application.
Step 14: Notice that now we have 2 tables generated by entity framework as expected.
 |
| 2 Tables Generated by Entity Framework |
Insert into Employees values ('Mark', 'Hastings', 'Male')
Insert into Employees values ('Steve', 'Pound', 'Male')
Insert into Employees values ('Ben', 'Hoskins', 'Male')
Insert into Employees values ('Philip', 'Hastings', 'Male')
Insert into Employees values ('Mary', 'Lambeth', 'Female')
Insert into EmployeeContactDetails values
(1, 'Mark@pragimtech.com', '111111111', '111111111')
Insert into EmployeeContactDetails values
(2, 'Steve@pragimtech.com', '2222222222', '2222222222')
Insert into EmployeeContactDetails values
(3, 'Ben@pragimtech.com', '3333333333', '3333333333')
Insert into EmployeeContactDetails values
(4, 'Philip@pragimtech.com', '44444444444', '44444444444')
Insert into EmployeeContactDetails values
(5, 'Mary@pragimtech.com', '5555555555', '5555555555')
Step 16: At this point run the application. Insert, update and delete an Employee, and notice that both the tables (Employees and EmployeeContactDetails) are updated as expected.
Output Should be look like following..
 |
| WebForm Output |
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