How to maintain class after button click on page - asp.net

Question

I have a page in ASP .NET where when I access it, programmatically I set a value in the TextBox. When I click on the Button, I would like to update that value, but it gives me error:
Object not defined
Here is my code:
public partial class InsertValues : System.Web.UI.Page
{
DataProvider dataProvider = new DataProvider(); // This class contains all the querys I need to pull data
public MyValuesClass myValues; // This is my class where I get the data from my DB
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
startMyPage(); // Function that gets the values from the DataBase and sets my TextBox with the values.
}
else
{
}
}
private void startMyPage()
{
myValues = dataProvider.getValuesFromDB(); // Function that gets the values from a query and put them in my class, the values are. String "Banana" and Bool isNew = True
if (!myValues.isNew) //
{
txtFood.Text = myValues.food
}
else
{
myValues= new myValues();
myValues.isNew = true;
}
}
protected void btnSave_Click(object sender, EventArgs e)
{
if (myValues.isNew) // Object not defined.
{
dataProvider.addMyValues(myValues); // It Inserts into my DB
}
else
{
dataProvider.editMyValues(myValues); // It Updates into my DB
}
}
}
Basically, after I click on my "btnSave" the class myValues becomes null, and I get the error Object not defined, is there a way to maintain the class Values?

Answer 1

You need to refetch your myValues object on PostBack.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
startMyPage();
}
else
{
myValues = dataProvider.getValuesFromDB();
}
}
Only data that's stored in the ViewState or equivalent persistence mechanism will be kept between the initial page load and post backs, which is why values of your webforms page controls are persisted, but your code behind property isn't.
You can store things manually in the ViewState like this: ViewState["someKey"] = someObject;, but someObject has to be serializable. It looks like myValues is an ORM object, so it probably isn't serializable.

Answer 2

All Variables are re-initiated at every post back. you better store your class public MyValuesClass myValues in session or viewstate.