Question

在使用MVVM时，我正在努力解决如何连接互连组合框的问题。我有一个代表订单的DTO，其中包含CustomerId和OrderTypeId。然后将这些包裹在OrderViewModel内。我还有一个EditOrderViewModel，它从db加载一个Customers列表。

我想要做的是从DB加载订单（类似于加载功能）在ComboBox中选择正确的项目（项目源是List，在文本中显示所选客户的名称）阻止组合框右侧，最后在下一个组合框中加载属于该Customer的OrderType列表，再次选择正确的OrderType，并在右侧的TextBlock中显示OrderTypeName。

当我从组合框中使用SelectedItem时，我设法让一些行为起作用，但这只是当我手动选择项时，因为我不确定在我的viewmodel中我如何转换Order.CustomerId（类型int）进入正确的SelectedItem（类型为CustomerDTO）。下面是一些代码，它们总体上显示了我在使用内存数据源时要实现的目标。谢谢Alex

        <ComboBox Height="25" Width="150"  ItemsSource="{Binding Path=Customers}" SelectedValue="{Binding Path=Order.CustomerId}" SelectedValuePath="Id">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                        <TextBlock Text="{Binding Path=Code}"></TextBlock>
                         <TextBlock Text="{Binding Path=Name}"></TextBlock>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
        <TextBlock Text="{Binding Path=Name,Mode=OneWay,NotifyOnSourceUpdated=True}"></TextBlock>

public class EditOrderViewModel : VMBase
    {
        public OrderViewModel Order{get;set;}

        public void Load()
        {
            Order = new OrderViewModel(new OrderDto{CustomerId=1,OrderTypeId=2});
            Order.PropertyChanged += MainWindowViewModel_PropertyChanged;
        }

        public EditOrderViewModel()
        {
            Order = new OrderViewModel(new OrderDto());
            Order.PropertyChanged += OrderViewModel_PropertyChanged;

            Customers = new List<CustomerDto> {  
            new CustomerDto{ Id = 1, Code = "ACME", Name = "ACME CORP" }, 
            new CustomerDto{ Id = 2, Code = "MSFT", Name="MICROSOFT CORP" }, 
            new CustomerDto{ Id = 3, Code = "APP", Name = "APPLE" }};

            OrderTypes = new List<OrderTypeDto>{
                new OrderTypeDto{OrderTypeId=1, CustomerId =1, Name = "Cake Order"},
                new OrderTypeDto{OrderTypeId=2, CustomerId =1, Name = "Sandwich                 Order"},
                new OrderTypeDto{OrderTypeId=3, CustomerId =2, Name = "Chocolate Order"},
                new OrderTypeDto{OrderTypeId=4, CustomerId =2, Name = "Bread Order"},
                new OrderTypeDto{OrderTypeId=5, CustomerId =3, Name = "Drinks Order"}};
        }

        void OrderViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            switch (e.PropertyName)
            {
                case "OrderTypeId":
                    break;
                case "SelectedCustomer":
                    break;
                default:
                    break;
            }
        }

        public List<OrderTypeDto> OrderTypes { get; set; }
        public List<CustomerDto> Customers { get; set; }
    }

    public class OrderDto
    {
        public int CustomerId { get; set; }
        public int OrderTypeId { get; set; }
    }

    public class CustomerDto
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Code { get; set; }
    }

    public class OrderViewModel : VMBase
    {
        private OrderDto _orderDto;
        private string _customerName;

        public OrderViewModel(OrderDto orderDto)
        {
            _orderDto = orderDto;
        }

        public int CustomerId {
            get { return _orderDto.CustomerId; }
            set
            {
                _orderDto.CustomerId = value;
                RaisePropertyChanged("CustomerId");
            }
        }

        public string CustomerName    {
            get { return _customerName; }
            set {_customerName = value; 
                RaisePropertyChanged("CustomerName");
            }
        }

        public int OrderTypeId
        {
            get { return _orderDto.OrderTypeId; }
            set
            {
                _orderDto.OrderTypeId = value;
                RaisePropertyChanged("OrderTypeId");
            }
        }
    }

Answer 1

不要在XAML绑定中设置ComboBox.SelectedValue。您应该将ComboBox.SelectedItem绑定到模型，以便轻松获得CustomDTO。您应该向OrderViewModel添加一个名为Customer（类型为CustomerDTO ）的属性，而不是尝试使用多个属性（ CustomerID，CustomerName等）重新创建CustomerDTO。）。

关于viewmodel和互连组合框的建议

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