C# 未创建Catel ViewModel

我有一个calel:Usercontrol，它将是一个带有重写的GetViewModelType（）方法的侧栏

此外，我还有dependencyProperty来设置模型项

问题是我的ViewModel从未初始化

我不知道为什么，但其他控件视图模型已正确初始化

我就是这样做的：

在父视图中：

<itemSideBar:ItemSidebarView Grid.Column="1" PlaceItem="{Binding ElementName=itemsList, Path=SelectedItem}"></itemSideBar:ItemSidebarView>

---

您正在另一个视图中使用该视图。请注意，Catel中的每个视图都有自己的视图模型

正如您在日志中所看到的，它首先尝试使用最多参数的构造函数（这与模型注入有关）。之后，它将使用空构造函数

在您的情况下，只需执行以下操作：

1） 删除空构造函数（您不希望视图模型没有上下文，对吗？）

2） 确保设置了有效的数据上下文。当前，数据上下文是父视图的上下文，父视图是父视图模型。在日志中，您可以看到，因为它说当前数据上下文是TabListViewModel，而您的构造函数需要类型为PlaceItem的模型

您可以如下设置数据上下文：

<itemSideBar:ItemSidebarView Grid.Column="1" DataContext="{Binding ElementName=itemsList, Path=SelectedItem}" />

using Catel.MVVM;

/// <summary>
/// UserControl view model.
/// </summary>
public class ItemSideBarViewModel : ViewModelBase
{
    public ItemSideBarViewModel()
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="ItemSideBarViewModel"/> class.
    /// </summary>
    public ItemSideBarViewModel(PlaceItem item)
    {
        PlaceItem = item;
    }

    /// <summary>
    /// Gets the title of the view model.
    /// </summary>
    /// <value>The title.</value>
    public override string Title { get { return "View model title"; } }

    /// <summary>
    /// Gets or sets the property value.
    /// </summary>
    [Model]
    public PlaceItem PlaceItem
    {
        get { return GetValue<PlaceItem>(PlaceItemProperty); }
        set { SetValue(PlaceItemProperty, value); }
    }

    /// <summary>
    /// Register the PlaceItem property so it is known in the class.
    /// </summary>
    public static readonly PropertyData PlaceItemProperty = RegisterProperty("PlaceItem", typeof (PlaceItem), null);

    // TODO: Register models with the vmpropmodel codesnippet
    // TODO: Register view model properties with the vmprop or vmpropviewmodeltomodel codesnippets
    // TODO: Register commands with the vmcommand or vmcommandwithcanexecute codesnippets
}

12:37:59:829 => [DEBUG] [Catel.IoC.TypeFactory] Creating instance of type 'EliteCard.ViewModels.TabList.ItemSideBar.ItemSideBarViewModel' using specific parameters. No constructor found in the cache, so searching for the right one
12:37:59:830 => [DEBUG] [Catel.IoC.TypeFactory] Checking if constructor 'public ctor(PlaceItem place)' can be used
12:37:59:830 => [DEBUG] [Catel.IoC.TypeFactory] Constructor is not valid because value 'EliteCard.ViewModels.TabList.TabListViewModel' cannot be used for parameter 'EliteCard.ViewModels.TabList.TabListViewModel'
12:37:59:831 => [DEBUG] [Catel.IoC.TypeFactory] The constructor is valid and can be used
12:37:59:831 => [DEBUG] [Catel.IoC.TypeFactory] No constructor could be used, cannot construct type 'EliteCard.ViewModels.TabList.ItemSideBar.ItemSideBarViewModel' with the specified parameters
12:37:59:832 => [DEBUG] [Catel.IoC.TypeFactory] Creating instance of type 'EliteCard.ViewModels.TabList.ItemSideBar.ItemSideBarViewModel'. No constructor found in the cache, so searching for the right one.
12:37:59:832 => [DEBUG] [Catel.IoC.TypeFactory] Calling constructor.Invoke with the right parameters
12:37:59:834 => [DEBUG] [Catel.MVVM.ViewModelBase] Creating view model of type 'ItemSideBarViewModel' with unique identifier 3

<itemSideBar:ItemSidebarView Grid.Column="1" DataContext="{Binding ElementName=itemsList, Path=SelectedItem}" />

var vm = ViewModel as ItemSideBarViewModel;
if (vm != null)
{
    var myPlaceItem = vm.PlaceItem;
}