Simple connection between SQL Server CE, Entity Framework, and WinForms

Question

I've created a simple Form containing two TextBoxes for name and age, and a button to submit. I added a "Local Database" to my project called Sample.sdf.

I've created a table called Customers and added three columns: Id, Name, and Age. I've set the Id column as the primary key but didn't set it as an identity column.

Then, I added an "ADO.NET Entity Data Model" called SampleEntities. I selected "Generate from database" and chose the Sample.sdf. I've selected the table and clicked Finish.

In my Button_Click event I've done:

using (SampleEntities se = new SampleEntities())
{
   Customer c = new Customer();
   c.Id = FindNextId();
   c.Age = Convert.ToDouble(txtAge.Text);
   c.Name = txtAge.Text;

   se.AddToCustomers(c);
   se.AcceptAllChanges();
   se.SaveChanges();
}
MessageBox.Show("Done");

I'm getting the "Done" message with no problems, but the records are not showing in the Server Explorer - Customers table - Show Table Data option.

Note: I know that in runtime, the sdf file is located in my debug folder. I'm checking both the sdf file in the project directory, and the sdf file in the debug folder, and neither have any records. Furthermore, I have set my sdf file property "Copy To Output Directory" to "Copy if newer".

So my question is, where is the customer row?

Dave Cousineau · Accepted Answer · 2014-07-31 11:00:42Z

2

The issue is your AcceptAllChanges call. You do not need to call it; just call SaveChanges.

using (SampleEntities se = new SampleEntities())
{
   Customer c = new Customer();
   c.Id = FindNextId();
   c.Age = Convert.ToDouble(txtAge.Text);
   c.Name = txtAge.Text;
   se.AddToCustomers(c);

   se.SaveChanges();
}
MessageBox.Show("Done");

You only need to call AcceptAllChanges if you call one of:

SaveChanges(false)
SaveChanges(SaveOptions.None)
SaveChanges(SaveOptions.DetectChangesBeforeSave)

When you call SaveChanges(), (with no arguments), "accepting all changes" happens automatically.

edited Jul 31, 2014 at 11:00

answered Jul 27, 2014 at 22:55

Dave Cousineau

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2 Comments

subirshan Over a year ago

You are right ! so please tell me what is the difference between AcceptAllChanges and SaveChanges ? And when I use each ?

Dave Cousineau Over a year ago

@subirshan Explained it a little in the answer. See Chris's answer, too, as well as this other question.

Chris · Accepted Answer · 2014-07-28 11:19:17Z

2

If you need to call the AcceptAllChanges method (1), you must save changes before accepting them.

se.SaveChanges();
se.AcceptAllChanges();

The AcceptAllChanges method iterates all the ObjectStateEntry objects within the ObjectStateManager that are Added or Modified, and then sets the state of the entry to Unchanged. The Deleted items become detached.

So when you call SaveChanges after AcceptAllChanges, there is nothing to save.

(1) As @Sahuagin pointed out, there is generally no need to call the AcceptAllChanges method. If you call SaveChanges() you don't need to call AcceptAllChanges at all.

You only must call the method when you use the SaveChanges(SaveOptions) method and do not specify the AcceptAllChangesAfterSave in SaveOptions.

edited Jul 28, 2014 at 11:19

answered Jul 27, 2014 at 21:57

Chris

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2 Comments

Dave Cousineau Over a year ago

From what I read here I think that calling AcceptAllChanges is only necessary if you called SaveChanges(false). If you call SaveChanges() or equivalently SaveChanges(true), you don't need to call AcceptAllChanges at all.

Chris Over a year ago

@Sahuagin You are right. Note, however, that the SaveChanges(Boolean) method is obsolete

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