“Two-way binding requires Path or XPath” when edit wpf datagrid

Question

ContractListUserControl.XAML

Answer 1

to achieve the initialization of Person property you may modify as follows

public class Contract
{
    public Contract()
    {
        Person = new Person();
    }

    public string RankName { get; set; }
    public string RankShortName { get; set; }
    public Person Person { get; set; }
}

add a constructor and initialize accordingly