"双向绑定需要路径或XPath"当编辑WPF数据网格 [英] "Two-way binding requires Path or XPath" when edit wpf datagrid

问题描述

ContractListUserControl.XAML

ContractListUserControl.XAML

<DataGrid AutoGenerateColumns="False"
              ItemsSource="{Binding Path=ContractList}"
              SelectedItem="{Binding Path=SelectedContract}">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding Path=Person.LastName}" Header="Last Name" />
            <DataGridTextColumn Binding="{Binding Path=Person.GivenName}" Header="Given Name" />
            <DataGridTextColumn Binding="{Binding Path=ContractStart, StringFormat=dd/MM/yyyy, Mode=TwoWay}" Header="Contract Start" />
            <DataGridTextColumn Binding="{Binding Path=ContractEnd, StringFormat=dd/MM/yyyy, Mode=TwoWay}" Header="Contract End" />
        </DataGrid.Columns>
</DataGrid>

Contract.cs

Contract.cs

public class Contract
{
    public DateTime ContractStart { get; set; }
    public DateTime ContractEnd { get; set; }
    public Person Person { get; set; }
}

Person.cs

Person.cs

public class Person
{
    public string LastName { get; set; }
    public string GivenName { get; set; }
}

ViewModel.cs

ViewModel.cs

public class ContractListViewModel : INotifyPropertyChanged
{
    private ObservableCollection<Contract> _contractList;
    public ObservableCollection<Contract> ContractList
    {
        get { return _contractList; }
        set { SetField(ref _contractList, value, () => ContractList); } // Same as OnPropertyChanged
    }

    private Contract _selectedContract;
    public Contract SelectedContract
    {
        get { return _selectedCrew; }
        set { SetField(ref _selectedCrew, value, () => SelectedCrew); }
    }
}

如果我设置DataGrid为只读，它的工作原理很好，问题是，当我直接编辑姓氏和给定名称DataGrid列，它会崩溃，并抛出消息InvalidOperationException异常双向绑定需要路径或XPath。但如果我只是编辑ContractStart和ContractEnd正常工作

If I set the datagrid as readonly, it works fine, problem is when I edit the LastName and GivenName DataGrid Column directly, it will crash, and throw the InvalidOperationException with message "Two-way binding requires Path or XPath". But if I just edit the ContractStart and ContractEnd it works fine.

我搜索了一些帮助，我想我遇到的这个家伙相同的情况：
的DataGrid - "双向绑定需要路径或XPath" <。 / A>

I searched for some help, and I think I meet the same situation with this guy: DataGrid - "Two-way binding requires Path or XPath."

所以问题是，这人属性为null，答案说我应该初始化结合在DataContext的，但没有说怎么对象要做到这一点。

So the problem is that the Person Property is null, and the answer said that I should initialize the object that binding in the DataContext but didn't say how to do that.

推荐答案

要实现个人财产的初始化，你可以修改如下：

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; }
}

添加一个构造函数并初始化相应

add a constructor and initialize accordingly

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