C# 从usercontrol datacontext属性初始化父ViewModel属性

我正在尝试从

usercontrol

属性初始化父

ViewModel

属性。。下面是快照。。。如果属性为

null

或

反之亦然，我想通过usercontrol初始化父属性“one”和“Two”

window.xaml

<Window x:Class="wpfParentUserControlDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:wpfParentUserControlDemo"
        mc:Ignorable="d"
        Title="MainWindow" Height="369.737" Width="525">
    <Window.DataContext>
        <local:ParentViewModel />
    </Window.DataContext>
    <Grid Margin="0,0,0,-4">        
        <local:UserControl1 DataContext="{Binding One}" Margin="288,49,22,240"></local:UserControl1>
        <local:UserControl1 DataContext="{Binding Two}" Margin="10,49,283,240"></local:UserControl1>
    </Grid>
</Window>

<UserControl x:Class="wpfParentUserControlDemo.UserControl1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:wpfParentUserControlDemo"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <ComboBox ItemsSource="{Binding Connections}" DisplayMemberPath="Name" ></ComboBox>
    </Grid>
</UserControl>

---

我不确定您想做什么，但如果您想检查

UserControl

的

DataContext

是否已设置，您应该等到它已加载

然后，您可以使用

window.GetWindow

方法访问父窗口的

DataContext

：

public UserControl1()
{
    InitializeComponent();
    this.Loaded += (s, e) =>
    {
        if (this.DataContext == null)
        {
            MainWindow parentWindow = Window.GetWindow(this) as MainWindow;
            if (parentWindow != null)
            {
                ParentViewModel parentViewModel = parentWindow.DataContext as ParentViewModel;
                if (parentViewModel != null)
                {
                    //set One or Two or do whatever you want to do here...
                }
            }
        }
    };
}

---

那么，为什么要在构造函数中设置UserControl1的DataContext属性？@mm8，因为我为DataContext属性发送null，所以您想在UserControl1的构造函数中设置ParentViewModel的一个和两个属性，或者您的问题是什么？@mm8是。。更新了问题，请检查

using System.Collections.ObjectModel;
using System.Data;
using System.Windows.Controls;

namespace wpfParentUserControlDemo
{
    /// <summary>
    /// Interaction logic for UserControl1.xaml
    /// </summary>
    public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();

            if (this.DataContext == null)
            {
                var ViewModel = new DemoUserMainViewModel();
                ViewModel.Connections = new ObservableCollection<DemoConnectionViewModel>();
                ViewModel.Connections.Add(new DemoConnectionViewModel { Name = "A", Type = SqlDbType.BigInt });
                ViewModel.Connections.Add(new DemoConnectionViewModel { Name = "B", Type = SqlDbType.Bit });
                ViewModel.Connections.Add(new DemoConnectionViewModel { Name = "C", Type = SqlDbType.NVarChar });

                this.DataContext = ViewModel;
            }
        }
    }

    public class DemoUserMainViewModel : BaseViewModel
    {
        private ObservableCollection<DemoConnectionViewModel> _Connections;

        public ObservableCollection<DemoConnectionViewModel> Connections
        {
            get { return _Connections; }
            set { _Connections = value; }
        }
    }

    public class DemoConnectionViewModel : BaseViewModel, IDataConnection
    {
        private string _Name;

        public string Name
        {
            get { return _Name; }
            set { _Name = value; }
        }

        private SqlDbType _Type;

        public SqlDbType Type
        {
            get { return _Type; }
            set { _Type = value; }
        }
    }
}

using System.Data;

namespace wpfParentUserControlDemo
{
    public interface IDataConnection
    {  
        string Name { get; set; }
        SqlDbType Type { get; set; }
    }
}

public UserControl1()
{
    InitializeComponent();
    this.Loaded += (s, e) =>
    {
        if (this.DataContext == null)
        {
            MainWindow parentWindow = Window.GetWindow(this) as MainWindow;
            if (parentWindow != null)
            {
                ParentViewModel parentViewModel = parentWindow.DataContext as ParentViewModel;
                if (parentViewModel != null)
                {
                    //set One or Two or do whatever you want to do here...
                }
            }
        }
    };
}