1. Simple Load and Bind Example
[sourcecode language=”vb.net”]
Dim AdventureWorks_DataEntity as New AdventureWorksDataEntities()
Dim Query = From e IN AdventureWorks_DataEntity.Employee
Gridview.DataSource = query
Gridview.databind()
[/sourcecode]
2. Load Related Data in Entity Framework
[sourcecode language=”vb.net”]
Dim AdventureWorks_DataEntity as New AdventureWorksDataEntities()
For Each employee in AdventureWorks_DataEntity.Employee
Dim Li as New ListItem()
Li.Text = employee.EmployeeID & ” ”
If (Not employee.EmployeePayHistory.IsLoaded) Then
employee.EmployeePayHistory.Load()
End if
For Each pay In employee.EmployeePayHistory
li.Text &= “Pay Rate: ” & pay.Rate & ” ”
Next pay
BulletedList1.Items.Add(li)
Next employee
[/sourcecode]
Another option for loading related data is to use the “include”. This will eager load the children EmployeePayHistory for the employees.
[sourcecode language=”vb.net”]
Dim AdventureWorks_DataEntity as New AdventureWorksDataEntities()
Dim query = from e in employee.Include(“EmployeePayHistory”)
[/sourcecode]
3. Singleton Reference (One to One) to get relationship use “objectReference”
[sourcecode language=”vb.net”]
var personTwo = (from p in context.Person WHERE p.Student != null select p).first();
personTwo.StudentReference.Load()
‘(one to Many relationship)
personTwo.Student.Load()
[/sourcecode]
4. Delete Entity
[sourcecode language=”C#”]
try
{
using (var context = new AdventureWorks2008Entities())
{
var prod = context.Products.Where(p => p.ProductID == 1005).First();
context.DeleteObject(prod);
context.SaveChanges();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.InnerException.Message);
}
[/sourcecode]
5.ATTACHING and DETACHING
If calls across assembly layer, it’s detached when accessed.
<asp:EntityDataSource Include=”Student”>
<asp:listview Id=”listView” runat=”server” DataKeyNames=”PersonID” DataSourceID=”personDataSource” Insert …
<%# Eval(“Student.Year”) %>
<asp:ObjectDataSource (Develop new class i.e. people.cs as partial class)
SchoolEntities context = new SchoolEntities();
return context.Person.INclude(“Student.Where(p => p.enrollmentdate.hasvalue.tolist();
6.POCO
Still to come…
