Master-Detail/Binding源代码问题

Question

我的DataGridViews都能正确显示父记录和子记录。我还可以成功地添加子记录并将它们保存回我的数据源(一个XML文件)。但是，当我尝试添加新的父项和子项时，我的程序抛出一个异常，说明即使细节DataGridView中存在子项记录，也没有要添加的子项记录。

因此，问题是当我的子记录是新的时，它们不会绑定到类。我遗漏了什么？

我的类结构如下：

public class Roads
{
   public string RoadName { get; set; }
   public List<CrossStreet> CrossStreets { get; set; }        
}

public class CrossStreet
{
   public string CrossStreetName { get; set;}
}

我有两个DataGridViews，我将我的类绑定到它们上，如下所示：

BindingSource roadBindingSource = new BindingSource();
BindingSource crossStreetBindingSource = new BindingSource();

// _roads contains both the road and cross street data.
roadBindingSource.DataSource = _roads;

crossStreetBindingSource.DataSource = roadBindingSource;
crossStreetBindingSource.DataMember = "CrossStreets";

dataGridViewRoads.DataSource = roadsBindingSource;
dataGridViewCrossStreets.DataSource = crossStreetBindingSource;

Answer 1

问题出在我的类实现上。而不是：

public class Roads
{
   public string RoadName { get; set; }
   public List<CrossStreet> CrossStreets { get; set; }        
}

public class CrossStreet
{
   public string CrossStreetName { get; set;}
}

我使用：

public class Roads
{
   private List<CrossStreets> _crossStreets = new List<CrossStreets>();
   public string RoadName { get; set; }
   public List<CrossStreet> CrossStreets { get { return _crossStreets;} }        
}

public class CrossStreet
{
   public string CrossStreetName { get; set;}
}