为什么这个视图没有正确绑定到这个ViewModel？ [英] Why is this View not correctly binding to this ViewModel?

问题描述

以下代码运行时没有错误，但我的列表框是空。

据我所知，我正确地说：

• 将View的DataContext设置为ViewModel本身（ DataContext = new CustomersViewModel（）; ）


• ViewModel中的客户对象（ public static ObservableCollection< Customer> GetAll（））


• 将ListBox绑定到客户对象（ ItemsSource ={Binding GetAll}）

的语法我错过这里？

CustomersView.xaml：

 < UserControl x：Class =TestDynamicForm123.View.CustomersView
 xmlns =http://schemas.microsoft.com/winfx/2006/xaml/presentation 
 xmlns：x =http://schemas.microsoft.com/winfx/2006/xaml& gt; 
< UserControl.Resources> 
< Style x：Key =allCustomersListBoxTargetType =ListBox> 
< Setter Property =BorderThicknessValue =0/> 
< / Style> 
< DataTemplate x：Key =allCustomersDataTemplate> 
< StackPanel Orientation =Horizo​​ntal> 
< TextBlock Text ={Binding FirstName}/> 
< TextBlock Text =/> 
< TextBlock Text ={Binding LastName}/> 
< / StackPanel> 
< / DataTemplate> 
< /UserControl.Resources> 
 
< StackPanel Style ={StaticResource viewWrappingStackPanel}> 
< ListBox ItemsSource ={Binding GetAll}
 ItemTemplate ={StaticResource allCustomersDataTemplate}
 Style ={StaticResource allCustomersListBox}> 
< / ListBox> 
< / StackPanel> 
< / UserControl> 
  

CustomersView.xaml.cs：

 使用System.Windows.Controls; 
使用TestDynamicForm123.ViewModel; 
 
命名空间TestDynamicForm123.View 
 {
 public partial class CustomersView：UserControl 
 {
 public CustomersView（）
 {
 InitializeComponent （）; 
 
 DataContext = new CustomersViewModel（）; 
} 
} 
} 
  

CustomersViewModel.cs ：

  using System.Collections.ObjectModel; 
 
命名空间TestDynamicForm123.ViewModel 
 {
 public class CustomersViewModel 
 {
 public static ObservableCollection< Customer> GetAll（）
 {
 return Customer.GetAll（）; 
} 
} 
} 
  

Customer.cs ：（模型）

 使用System.Collections.ObjectModel; 
 
命名空间TestDynamicForm123.ViewModel 
 {
 public class Customer 
 {
 public int Id {get;组; } 
 public string FirstName {get;组; } 
 public string LastName {get;组; } 
 public int Age {get;组; } 
 
 public static ObservableCollection< Customer> GetAll（）
 {
 ObservableCollection< Customer> customers = new ObservableCollection< Customer>（）; 
 customers.Add（new Customer（）{FirstName =Jay，LastName =Anders，Age = 34}）; 
 customers.Add（new Customer（）{FirstName =Jim，LastName =Smith，Age = 23}）; 
 customers.Add（new Customer（）{FirstName =John，LastName =Jones，Age = 22}）; 
 customers.Add（new Customer（）{FirstName =Sue，LastName =Anders，Age = 21}）; 
 customers.Add（new Customer（）{FirstName =Chet，LastName =Rogers，Age = 35}）; 
 customers.Add（new Customer（）{FirstName =James，LastName =Anders，Age = 37}）; 
回报客户; 
} 
 
} 
} 
  

解决方案

问题是您尝试绑定到CustomerViewModel.GetAll（），当CustomerViewModel中的GetAll是静态函数而不是实例属性时。

将静态函数更改为这样（在CustomerViewModel中）：

  public ObservableCollection< Customer> GetAll 
 {
 get {return Customer.GetAll（）; } 
} 
  

I'm trying to bind my view to my view model without DataObjectProvider.

The following code runs without an error, but my ListBox is empty.

As far as I can tell, I correctly:

• set the View's DataContext to the ViewModel itself (DataContext = new CustomersViewModel();)
• expose the customer objects in the ViewModel (public static ObservableCollection<Customer> GetAll())
• bind the ListBox to the customer objects (ItemsSource="{Binding GetAll}")

What little piece of syntax am I missing here?

CustomersView.xaml:

<UserControl x:Class="TestDynamicForm123.View.CustomersView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <UserControl.Resources>
        <Style x:Key="allCustomersListBox" TargetType="ListBox">
            <Setter Property="BorderThickness" Value="0"/>
        </Style>
        <DataTemplate x:Key="allCustomersDataTemplate">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding FirstName}"/>
                <TextBlock Text=" "/>
                <TextBlock Text="{Binding LastName}"/>
            </StackPanel>
        </DataTemplate>
    </UserControl.Resources>

    <StackPanel Style="{StaticResource viewWrappingStackPanel}">
        <ListBox ItemsSource="{Binding GetAll}"
                 ItemTemplate="{StaticResource allCustomersDataTemplate}"
                 Style="{StaticResource allCustomersListBox}">
        </ListBox>
    </StackPanel>
</UserControl>

CustomersView.xaml.cs:

using System.Windows.Controls;
using TestDynamicForm123.ViewModel;

namespace TestDynamicForm123.View
{
    public partial class CustomersView : UserControl
    {
        public CustomersView()
        {
            InitializeComponent();

            DataContext = new CustomersViewModel();
        }
    }
}

CustomersViewModel.cs:

using System.Collections.ObjectModel;

namespace TestDynamicForm123.ViewModel
{
    public class CustomersViewModel
    {
        public static ObservableCollection<Customer> GetAll()
        {
            return Customer.GetAll();
        }
    }
}

Customer.cs: (model)

using System.Collections.ObjectModel;

namespace TestDynamicForm123.ViewModel
{
    public class Customer
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Age { get; set; }

        public static ObservableCollection<Customer> GetAll()
        {
            ObservableCollection<Customer> customers = new ObservableCollection<Customer>();
            customers.Add(new Customer() { FirstName = "Jay", LastName = "Anders", Age = 34 });
            customers.Add(new Customer() { FirstName = "Jim", LastName = "Smith", Age = 23 });
            customers.Add(new Customer() { FirstName = "John", LastName = "Jones", Age = 22 });
            customers.Add(new Customer() { FirstName = "Sue", LastName = "Anders", Age = 21 });
            customers.Add(new Customer() { FirstName = "Chet", LastName = "Rogers", Age = 35 });
            customers.Add(new Customer() { FirstName = "James", LastName = "Anders", Age = 37 });
            return customers;
        }

    }
}

解决方案

The problem is that you are trying to bind to CustomerViewModel.GetAll(), when GetAll in CustomerViewModel is a static function not an instance property.

Change the static function to something like this (in CustomerViewModel):

public ObservableCollection<Customer> GetAll
{
    get { return Customer.GetAll(); }
}

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