c# - ComboBox onChange 后 TextBox 不显示值(WPF、C#、Binding)

Question

我的 UserControl 包含 ComboBox 和 TextBox:

 <ComboBox x:Name="cmbId" SelectionChanged="cmbId_SelectionChanged" />
 <TextBox x:Name="txb1" Visibility="Hidden" Text="{Binding Path=FirstName, UpdateSourceTrigger=PropertyChanged}" />

我已将值加载到 ComboBox:

  public MyDataView()
  {
            InitializeComponent();
            MyDBViewDataContext mydata = new MyDBViewDataContext();
            cmbId.ItemsSource = (from q in mydata.test_views
                                        select q.Id).ToList();
  }

当用户在 ComboBox 上选择项目时，TextBox 应显示值:

private void cmbId_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
            int myId = 0;
            Int32.TryParse(cmbId.Text, out myId);

            txb1.Visibility = Visibility.Visible;

            MyDBViewDataContext myDataList = new MyDBViewDataContext();
            var queryAll = (from q in myDataList.test_views
                        where q.Id.Equals(myId)
                        select q);
 }

但它不起作用。缺少什么或我做错了什么？

Answer 1

如果两者都是Id和 FirstName是您的实体类的属性，您可以设置 ItemsSource ComboBox 的属性(property)到IEnumerable<YourEntityType>并绑定(bind) Text TextBox 的属性(property)到 FirstName SelectedItem 的属性(property)的 ComboBox :

public MyDataView()
{
    InitializeComponent();
    MyDBViewDataContext mydata = new MyDBViewDataContext();
    cmbId.ItemsSource = (from q in mydata.test_views
                         select q).ToList();
}

<ComboBox x:Name="cmbId" DisplayMemberPath="Id"/>
<TextBox x:Name="txb1" Visibility="Hidden" Text="{Binding Path=SelectedItem.FirstName, UpdateSourceTrigger=PropertyChanged, ElementName=cmbId}" />

那么就不需要处理SelectionChanged了完全没有事件。

另一种选择是实际设置 Text TextBox 的属性(property)在事件处理程序中:

txb1.Text = var queryAll = (from q in myDataList.test_views
                    where q.Id.Equals(myId)
                    select q.FirstName).FirstOrDefault();