SaveChanges() not working with updating data

Kourosh94 · September 20th, 2013, 01:57 PM

Hi, this is my first post in this forum, So before anything I have to thank Mr.Spaanjaars for writing such a nice asp.net book...
.....
Here is my problem, I can insert records , delete them, but I can't update them

this is my code for updating a table named Assemble :

using (CostPriceEntities myEntities = new CostPriceEntities())
{
Assemble edit = (from a in myEntities.Assembles
where a.Id == _id
select a).SingleOrDefault();
if (edit != null)
{
edit.CodeA = tbCode.Text;
edit.MESCA = tbMESC.Text;
edit.NameA = tbName.Text;
edit.SpecificationA = tbSpecification.Text;
edit.ZaribA = Convert.ToDouble(tbZarib.Text);
edit.UpdateTimeA = DateTime.Now;
myEntities.SaveChanges();
}

it doesn't give me any error... but I can't figure out why it's not working!!!
I have to mention that just UpdateTimeA will update and others not...
sorry if my English is bad... Please tell me if I have to post more information...
Thanks again;)

Imar · September 20th, 2013, 02:18 PM

Hi there,

Quote:

So before anything I have to thank Mr.Spaanjaars for writing such a nice asp.net book...

Thank you. Glad you like it.

Are you sure that the query returns an object? Maybe _id doesn't have a valid value so edit is always null and the code in the if block never fires?

Quote:

I have to mention that just UpdateTimeA will update and others not...

Not sure what you mean with this. Can you give an example?

Imar

Kourosh94 · September 20th, 2013, 02:32 PM

Hi again, thanks for answering...

_id has a valid value, it's getting value here in page_load and after that elements in Page take value :

protected void Page_Load(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(Request.QueryString.Get("Id ")))
{
_id = Convert.ToInt32(Request.QueryString.Get("Id"));
}
using (CostPriceEntities myEntities = new CostPriceEntities())
{
// Assemble Info
var Ainfo = (from a in myEntities.Assembles
where a.Id == _id
select a).Single();
tbCode.Text = Ainfo.CodeA;
tbMESC.Text = Ainfo.MESCA;
tbName.Text = Ainfo.NameA;
tbSpecification.Text = Ainfo.SpecificationA;
tbZarib.Text = Ainfo.ZaribA.ToString();

// lCreate and lUpdate are Labels for showing datetime and lKind is a label just for getting the kind of Assemble from Assemble Table in database... not important...

lCreate.Text = Ainfo.CreateTimeA.ToString();
lUpdate.Text = Ainfo.UpdateTimeA.ToString();
lKind.Text = Ainfo.KindA;
}
}

Then I change some value in TextBox es and click on :
protected void bDoEdit_Click(object sender, EventArgs e)
{
using (CostPriceEntities myEntities = new CostPriceEntities())
{
Assemble edit = (from a in myEntities.Assembles
where a.Id == _id
select a).SingleOrDefault();
if (edit != null)
{
edit.CodeA = tbCode.Text;
edit.MESCA = tbMESC.Text;
edit.NameA = tbName.Text;
edit.SpecificationA = tbSpecification.Text;
edit.ZaribA = Convert.ToDouble(tbZarib.Text);
edit.UpdateTimeA = DateTime.Now;
myEntities.SaveChanges();
}
}
}

and for update example, I can tell you from the code above, just edit.UpdateTimeA = DateTime.Now is working and will update the time...
if I have to bring more information, Please tell me...

thanks again:)

Kourosh94 · September 20th, 2013, 03:06 PM

I found how to solve the problem, but I can't figure it out why the cause of problem...

I just add in Page_Load event :

if (!Page.IsPostBack && _id > -1)
{
using (CostPriceEntities myEntities = new CostPriceEntities())
{
// Assemble Info
var Ainfo = (from a in myEntities.Assembles
where a.Id == _id
select a).Single();
tbCode.Text = Ainfo.CodeA;
tbMESC.Text = Ainfo.MESCA;
tbName.Text = Ainfo.NameA;
tbSpecification.Text = Ainfo.SpecificationA;
tbZarib.Text = Ainfo.ZaribA.ToString();
lCreate.Text = Ainfo.CreateTimeA.ToString();
lUpdate.Text = Ainfo.UpdateTimeA.ToString();
lKind.Text = Ainfo.KindA;
}
}

It means I just add the : if (!Page.IsPostBack && _id > -1)

can anyone tell me the what's the problem?? it's because of view state??? I don't know!!!

Imar · September 20th, 2013, 03:08 PM

Ah, I see. The code in Page_Load overwrites the changes the user made with the data from the database, resulting in no change. Wrap the code that fills the controls in an if (!Page.IsPostBack) block and it should work:

Code:

if (!Page.IsPostBack)
{
  using (CostPriceEntities myEntities = new CostPriceEntities())
  {
  // Assemble Info
  var Ainfo = (from a in myEntities.Assembles
                                    where a.Id == _id
       select a).Single();
                   tbCode.Text = Ainfo.CodeA;
  tbMESC.Text = Ainfo.MESCA;
  tbName.Text = Ainfo.NameA;
                
  // Rest of the code here
  }
}

Hope this helps,

Imar

Imar · September 20th, 2013, 03:09 PM

Oh, looks like you already found it out.... ;-)

Imar

Kourosh94 · September 20th, 2013, 03:14 PM

Thank you so much Mr.Spaanjaars...
You and your book help me a lot... ;)