Vista - Link to Sql - Problems on Updating Database

Hello Everyone, I'm quite new to Linq and have had some problems updating my dabase.
I don't know if it is actually happening for be using a global data context or I'm missing something.
I have my typed DataContex and one Static Public Var to initialize it located within the namespace AlpaCommon, like following:


***********************My partial datacontext*******************

// partial datacontext class
namespace
AlpaCommon
{
public partial class AlpaDataContext : System.Data.Linq.DataContext
{

//Insert method is working...
public void InsertAnimal2(Animal instance)
{
Animais.InsertOnSubmit(instance);
SubmitChanges();
}

//Delete method is working...
public void DeleteAnimal2(int animalID)
{
var animal = (from a in Animais where a.AnimalID == animalID select a).First();
Animais.DeleteOnSubmit(animal);
SubmitChanges();
}

//Update method IS NOT working...
public void UpdateAnimal2(Animal newAnimal)
{
var animal = (from a in Animais where a.AnimalID == newAnimal.AnimalID select a).First();
animal = newAnimal;
SubmitChanges();
}


*****This is where I'm instanciating the datacontext e other variables I'll need in the whole app***


//global DataContext instance
namespace AlpaCommon
{
public static class Globals
{
public static AlpaDataContext db = new AlpaDataContext();


******************* This is the call to the update method **************

....................
....................
using AlpaCommon;
namespace Animais
{
public partial class Altera : System.Web.UI.Page
{
....................
....................
....................
....................
protected void btnUpdate_Click(object sender, EventArgs e)
{
try
{
//cria um novo Objeto do tipo Animal
Animal animalAltera = new Animal();
//set new values
animalAltera.AnimalID = Convert.ToInt32(Request.Params["AnimalID"]);
animalAltera.Castrado = CastradoCheckBox.Checked;
animalAltera.DisponivelAdocao = DisponivelCheckBox.Checked;
animalAltera.Adotado = AdotadoCheckBox.Checked;
animalAltera.Nome = NomeTextBox.Text;
animalAltera.Tipo = TipoDropDownList.SelectedValue;
animalAltera.Sexo = SexoDropDownList.SelectedValue;
animalAltera.Descricao = DescricaoTextBox.Text;
animalAltera.Local = LocalTextBox.Text;
animalAltera.Foto = AlteraFoto();

AlpaCommon.Globals.db.UpdateAnimal2(animalAltera);
redirect = redirectSucesso;

}
catch
{
redirect = redirectErro;
}
finally
{
Helper.Redirect(redirect);
}
}


******************************************************************************************

I'm not catching any exception, it just does not update the database.
Am I missing something in my updating or calling method?
I'm looking forward for suggestions.

Thank you

Josimari Martarelli