ASP.NET 4.0 and the Entity Framework 4 - Part 2: Perform CRUD Operations Using the Entity Framework 4
page 6 of 8
by Vince Varallo
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Step 5: Retrieving a Single Record

We still have to add the code so that when a user selects an item in the drop down list the system will retrieve the record and display the information on the web page.  This will be done in the SelectedIndexChanged event.

1.    Switch back to Design view and double click on the Users drop down list.  This should create the SelectedIndexChanged event handler.

2.    Add the following code.

if (ddlUsers.SelectedValue == "")
{
  txtFirstName.Text = "";
  txtLastName.Text = "";
  lblInserted.Text = "";
  lblUpdated.Text = "";
}
else
{
  //Get the user from the DB
  using (OrderDBContainer db = new OrderDBContainer())
  {
    int userAccountId = Convert.ToInt32(ddlUsers.SelectedValue);    
    List<UserAccount> userAccounts = (from u in db.UserAccounts
                                                       where u.Id == userAccountId
                                                       select u).ToList();
 
    if (userAccounts.Count() > 0)
    {
      UserAccount userAccount = userAccounts[0];
      txtFirstName.Text = userAccount.FirstName;
      txtLastName.Text = userAccount.LastName;
      lblInserted.Text = userAccount.AuditFields.InsertDate.ToString();
      lblUpdated.Text = userAccount.AuditFields.UpdateDate.ToString();
    }
    else
    {
      //Error: didn't find user.
      txtFirstName.Text = "";
      txtLastName.Text = "";
      lblInserted.Text = "";
      lblUpdated.Text = "";
    }
  }
}

This code uses another LINQ query to retrieve a single record from the database based on the Id of the selected item in the drop down list.  If the record is found then the userAccounts count property would be greater than one.  You can then access the object by using the indexer.  The textboxes and labels are set to the properties of the object.

If you run the project now you should be able to pull up the records that were added previously and then update them.


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User Comments

Title: oussama   
Name: skksll
Date: 2012-11-26 9:58:51 AM
Comment:
great
Title: Very Good Article   
Name: cafeasp
Date: 2012-06-25 11:07:38 AM
Comment:
I just try the 'Update' code and it works perfect!

Thanks for sharing this info.
Title: Help there are erros in executing the sql file   
Name: Silver
Date: 2012-01-27 12:42:52 AM
Comment:
Msg 911, Level 16, State 1, Line 1
Database 'OrderSystem' does not exist. Make sure that the name is entered correctly.
Msg 262, Level 14, State 1, Line 17
CREATE TABLE permission denied in database 'master'.
Msg 262, Level 14, State 1, Line 3
CREATE TABLE permission denied in database 'master'.
Msg 4902, Level 16, State 1, Line 7
Cannot find the object "dbo.UserAccounts" because it does not exist or you do not have permissions.
Msg 4902, Level 16, State 1, Line 3
Cannot find the object "dbo.Addresses" because it does not exist or you do not have permissions.
Msg 4902, Level 16, State 1, Line 7
Cannot find the object "dbo.Addresses" because it does not exist or you do not have permissions.
Title: images   
Name: k k h
Date: 2011-12-09 2:25:39 PM
Comment:
Images are broken.
Title: CRUD operation   
Name: Suvashis
Date: 2011-04-07 6:45:55 AM
Comment:
Lots of thanks for the EF 4.0 CRUD Operation understanding
Title: You are the man   
Name: LukTar
Date: 2011-02-07 5:19:08 PM
Comment:
Big respect for YOU. Great article which helped me a lot.
Title: Great Work   
Name: Mayank
Date: 2010-10-29 4:26:15 AM
Comment:
It very helpful article to understand the initial CRUD operations using Entity Framework 4

Thanks a lot
Title: trusted   
Name: david zing
Date: 2010-07-05 7:35:59 PM
Comment:
ent:
I can´t use the lines the code below to update the entity:

db.UserAccounts.Attach(userAccount);
db.ObjectStateManager.ChangeObjectState(userAccount, System.Data.EntityState.Modified);

on the first line I get the message: Attach is not a member of System.Data.Objects.ObjectQuery(Of...)

What´s wrong ?
Title: Mr   
Name: David Zing
Date: 2010-06-09 6:52:52 AM
Comment:
I can´t use the lines the code below to update the entity:

db.UserAccounts.Attach(userAccount);
db.ObjectStateManager.ChangeObjectState(userAccount, System.Data.EntityState.Modified);

on the first line I get the message: Attach is not a member of System.Data.Objects.ObjectQuery(Of...)

What´s wrong ?
Title: N-Tier?   
Name: V. Jenks
Date: 2010-05-10 10:43:30 AM
Comment:
I'd love to see an article this straightforward and approachable in an n-tier tutorial? The EF seems very simple until you try and separate concerns. What if I'd like to store all of my business logic and data access in a separate class library project?
Title: Very good intro   
Name: Marshall
Date: 2010-05-05 2:23:05 PM
Comment:
Great intro to EF and made very simple to understand.
Title: Thanks   
Name: Soyka
Date: 2010-05-05 1:30:11 AM
Comment:
I'm coding just for fun and sometimes I don't know where to start with a new thing. Your articles put me on the right track...Thanks
Title: Far Too Good   
Name: Sreedevi
Date: 2010-03-31 7:14:48 AM
Comment:
This is a very nice article. Its seems like a cake walk creating applications using VS2010. Hope we get to work on VS 2010 very soon.

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