remove contracting wpf controlling code

i databinding displaying information textbox. i'm fundamentally doing like:

 open vacant showrandomobject(irandomobject randomobject) {
        contracting binding = new contracting {source = randomobject, route = new propertypath("name")};
        txtname.setbinding(textbox.textproperty, binding);
    }

i can't seem proceed unset binding. i job slight lot opposite objects nonetheless textbox sojourn same. there proceed mislay before contracting finished automatically i set new binding?