C# - Declare And Create Variable In Code Behind?

Here are 3 scenarios:

namespace NS
{
public partial class A: System.Web.UI.UserControl
private Variable v;
protected void Page_Load(object sender, EventArgs e){
if (!Page.IsPostBack) v= new Variable();
....
}
}
namespace NS
{
public partial class A: System.Web.UI.UserControl
private Variable v = new Variable();
protected void Page_Load(object sender, EventArgs e){
}
}
namespace NS
{
public partial class A: System.Web.UI.UserControl
private Variable v;
protected void Page_Load(object sender, EventArgs e){
v = new Variable();
}
}

When does the variable "v" gets created every time for the 2nd scenario? Is the 2st scenario is equivalent to the 3rd one?