Getting the text of the selecteditem in Combobox

When you look at the Text property in the SelectionChanged event of the ComboBox it returns the prior value
here is a way to get the right value (cb1 is the name of the ComboBox)

Add this in Window loaded event

DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(ComboBox.TextProperty, typeof(ComboBox));

dpd.AddValueChanged(cb1, OnTextChanged);
 

and here is the handler

private void OnTextChanged(object sender, EventArgs args)
        {
            MessageBox.Show(cb1.Text);
        }