绑定到嵌套属性仅显示列表中的第一项 [英] Binding to nested property only showing first item in list

问题描述

我试图将.NET 4.5中C#Winforms中的ListBox控件绑定到具有嵌套属性的对象列表，该属性希望用于DisplayMember.除了将DisplayMember设置为nested属性时，列表框仅显示一项，即使列表中有两项绑定到该列表项，它的工作方式也是如此.如果我注释掉用于设置DisplayMember的代码，则listBox将显示两个项目.这是框架中的错误吗?如果可以的话，我想避免添加其他属性或覆盖ToString()，因为我正在实现MVP，并且希望使视图逻辑与视图保持隔离.这是下面的一些示例代码.

I am trying to bind a ListBox Control in C# Winforms in .NET 4.5 to a list of objects that have a nested property that I wish to use for a DisplayMember. It sort of works except that when I set the DisplayMember to the nested property the listbox only shows one item even though there are two items in the list that it is bound to. If I comment out the code for setting the DisplayMember the listBox shows two items. Is this a bug in the framework? I would like to avoid adding another property or overriding ToString() if I can since I am implementing MVP and would like to keep my view logic isolated to my view. Here is some example code below.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        var bindingSource = new BindingSource();
        var listOfMyItems = new BindingList<MyItem>
        { 
          new MyItem { Number = 1, NestedItem = new NestedItem { Name = "name1", Note = "note1" } },
          new MyItem { Number = 2, NestedItem = new NestedItem { Name = "name2", Note = "note2" } },
        };
        bindingSource.DataSource = listOfMyItems;
        listBox1.DataSource      = bindingSource;
        //comment out the line below and the listBox1 will show 2 items
        listBox1.DisplayMember   = "NestedItem.Name";
    }
}
public class NestedItem
{
    public string Name { get; set; }
    public string Note { get; set; }
}
public class MyItem
{
    public NestedItem NestedItem { get; set; }
    public int Number { get; set; }
}

推荐答案

似乎将DisplayMember设置为"NestedItem.Name"仅显示SelectedItem-的NestedItem.Name属性，如果SelectedItem，我对此进行了测试更改后，显示的名称也会相应更改-.最简单的解决方法是为DisplayMember添加另一个属性:

It seems that setting DisplayMember to "NestedItem.Name" only displaying NestedItem.Name property of SelectedItem -I tested this, if SelectedItem changed, the Name displayed also changed accordingly-. The easiest work around is to add another property for DisplayMember :

public class MyItem
{
    public NestedItem NestedItem { get; set; }
    public int Number { get; set; }
    public String NestedItemName { get { return NestedItem.Name; } }
}

然后设置DisplayMember:

listBox1.DisplayMember   = "NestedItemName";

不雅致，但比在此处或 更新:

以下是我所做的一项快速测试.添加一个按钮以切换listBox1's DisplayMember. Onclick事件处理程序:

Following is a quick test I did. Add a button to toggle listBox1's DisplayMember. Onclick event handler :

listBox1.DisplayMember = (listBox1.DisplayMember == "Number") ? "NestedItem.Name" : "Number";

当DisplayMember设置为数字"时，您可以选择列表中的任何项目-不一定是第一项-，然后再次单击按钮.您会看到显示SelectedItem's NestedItem.Name.

when DisplayMember set to "Number" you can choose any item in list -not necessarily the first item-, then click the button again. You'll see that SelectedItem's NestedItem.Name displayed.

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