How to set the id android

gistfile1.txt

<Button
    android:text="Action 1"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:id="@+id/action1_button"
    android:layout_weight="1"
    android:layout_marginLeft="5dp" />
    

_app.Query(c=>c.Marked("action1_button"));

How do this on code ??? 

var btn = new Button();
//btn.SetID("action1_button"); ????