WPF TextBlock Width and Height

TextBlock t = new TextBlock()
{
    Width = 280,
    TextWrapping = System.Windows.TextWrapping.Wrap,
    FontSize = 12,
    Tag = foundClosureDay.CurrentDate,
    ToolTip = Persians.JulianToHijri(foundClosureDay.CurrentDate).DateToString
};
t.Text = "bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla ";

double height = t.Height;

height = t.ActualHeight;