****
我原先想实现的功能就是一个模块就是一个插件，所有插件加载到主界面的TreeView导航中，点击对应的项，显示对应的页面，而TreeView的集合并非我手动一个一个new TreeViewItem 是根据每个页面的元数据来生成
后来我也确实部分实现了这个小需求，但是不能做成无限极树，而且在用CustomExportMetadata设置元数据时也非常不合理,只能删掉然后一个一个new TreeViewItem了 (╯‵□′)╯︵┻━┻（菜鸡的无能狂怒）
****
****MEF需要用到的dll****
****注意****
插件没加载进去先看看查找插件dll的路径对不对
在Core类库中定义一个视图IView接口
public interface IView
{
//约束插件类型
//我并不关心你的class叫什么名字，我只需要知道谁继承了这个接口，然后我就可以转换成IView类型的。
//这难道就是传说中的面向接口编程??
}定义一个元数据IMetaData接口 (根据你的需要定义元数据)
/// <summary>
/// 优先级
/// </summary>
[DefaultValue(0)]
int Priority { get; }
/// <summary>
/// 名称（不能重复）
/// </summary>
string Name { get; }
/// <summary>
/// 描述
/// </summary>
string Description { get; }
/// <summary>
/// 作者
/// </summary>
string Author { get; }
/// <summary>
/// 版本
/// </summary>
string Version { get; }实现元数据接口的特性
[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
public class CustomExportMetadata : ExportAttribute, IMetaData
{
/// <summary>
/// 优先级
/// </summary>
public int Priority { get; private set; }
/// <summary>
/// 名称
/// </summary>
public string Name { get; private set; }
/// <summary>
/// 描述
/// </summary>
public string Description { get; private set; }
/// <summary>
/// 作者
/// </summary>
public string Author { get; private set; }
/// <summary>
/// 版本
/// </summary>
public string Version { get; private set; }
/// <summary>
/// 构造函数
/// </summary>
public CustomExportMetadata() : base(typeof(IMetaData))
{
this.UId = Guid.NewGuid().ToString();
}
/// <summary>
/// 构造函数
/// </summary>
public CustomExportMetadata() : base(typeof(IMetaData))
{
}
/// <summary>
/// 构造重载
/// </summary>
/// <param name="priority">优先级</param>
public CustomExportMetadata(int priority) : this()
{
this.Priority = priority;
}
// <summary>
/// 构造重载
/// </summary>
/// <param name="priority">优先级</param>
/// <param name="name">名称</param>
public CustomExportMetadata(int priority, string name) : this(priority)
{
this.Name = name;
}
/// <summary>
/// 构造重载
/// </summary>
/// <param name="priority">优先级</param>
/// <param name="name">名称</param>
/// <param name="description">描述</param>
public CustomExportMetadata(int priority, string name,string description) : this(priority, name)
{
this.Description = description;
}
/// <summary>
/// 构造重载
/// </summary>
/// <param name="priority">优先级</param>
/// <param name="name">名称</param>
/// <param name="description">描述</param>
/// <param name="author">作者</param>
public CustomExportMetadata(int priority, string name,string description,string author) : this(priority, name, description)
{
this.Author = author;
}
/// <summary>
/// 构造重载
/// </summary>
/// <param name="priority">优先级</param>
/// <param name="name">名称</param>
/// <param name="description">描述</param>
/// <param name="author">作者</param>
/// <param name="version">版本</param>
public CustomExportMetadata(int priority, string name,string description,string author,string version) : this(priority, name, description, author)
{
this.Version = version;
}在你想被加载的UserControl.xaml.cs里继承IView并添加Export和CustomExportMetadata特性
Export的参数是声明你要把这个类导出为什么类型
CustomExportMetadata的参数对照上面的重载
我们知道MEF作为IOC的方式之一，它的主要作用是解耦，MEF加上面向接口编程，可以使得你的设计更加灵活。我们知道类的构造函数是可以重载的，我们通过构造函数可以向对象传递参数。那么如果我们的MEF也需要通过构造函数传参怎么办呢？别担心，有我们神奇的ImportingConstructor为您解决.
[https://www.cnblogs.com/landeanfen/p/4848885.html](https://www.cnblogs.com/landeanfen/p/4848885.html)
/// <summary>
/// TestPluginsUserControl.xaml 的交互逻辑
/// </summary>
[Export(typeof(IView))]
[CustomExportMetadata(1, "测试模块1下的第一个页面", "测试模块1下的第一个页面", "HFMS","0.0.1")]
public partial class TestPluginsUserControl : UserControl, IView
{
[ImportingConstructor]
public TestPluginsUserControl()
{
InitializeComponent();
}
}定义TreeItem类
public class TreeItem
{
public int Id { get; set; }
public int ParentId { get; set; }
public string Name { get; set; }
public List<TreeItem> Nodes { get; set; }
}在主窗体的ViewModel里加载插件（延迟加载和普通加载）这里用的是懒加载（延迟加载） 普通加载请点击最下方链接
private List<TreeItem> _tvModel;
/// <summary>
/// TreeView的ItemSource
/// </summary>
public List<TreeItem> TVModel
{
get { return _tvModel; }
set { Set(ref _tvModel, value); }
}
private ObservableCollection<TabItem> _tabItemTests = new ObservableCollection<TabItem>();
/// <summary>
/// TabControl的ItemSource
/// </summary>
public ObservableCollection<TabItem> TabItemTests
{
get { return _tabItemTests; }
set { Set(ref _tabItemTests, value); }
}
//你要导入的类型和元数据数组，所有继承IView接口并导出的页面都在这个数组里
//后面参数也不知道有啥用，还在学习中
[ImportMany(typeof(IView),AllowRecomposition = true)]
private Lazy<IView, IMetaData>[] Plugins { get; set; }
private CompositionContainer container = null;
//窗体加载时调用的方法
private void ExcuteLoadWindow()
{
//获取工作目录
var dir = new DirectoryInfo(AppDomain.CurrentDomain.BaseDirectory);
if (dir.Exists)
{
//就是这里，读取所有符合条件的dll
var catalog = new DirectoryCatalog(dir.FullName, "MEF.*.dll");
container = new CompositionContainer(catalog);
try
{
//从特性化对象的数组创建可组合部件，并在指定的组合容器中组合这些部件。
container.ComposeParts(this);
}
catch (CompositionException ce)
{
Console.Write(ce.Message);
}
//排个序，我寻思着是不是有的插件还依赖着别的插件，所以需要排序
Plugins.OrderBy(p => p.Metadata.Priority);
//传个最顶级的节点id和创建好的节点集合
TVModel = GetTrees(0,SetTrees());
}
}
/// <summary>
/// 递归生成树结构
/// </summary>
/// <param name="parentid">父节点Id</param>
/// <param name="nodes">节点集合</param>
/// <returns></returns>
public List<TreeItem> GetTrees(int parentid, List<TreeItem> nodes)
{
List<TreeItem> mainNodes = nodes.Where(x => x.ParentId == parentid).ToList<TreeItem>();
List<TreeItem> otherNodes = nodes.Where(x => x.ParentId != parentid).ToList<TreeItem>();
foreach (TreeItem dpt in mainNodes)
{
dpt.Nodes = GetTrees(dpt.Id, otherNodes);
}
return mainNodes;
}
public List<TreeItem> SetTrees()
{
//这里创建节点集合
List<TreeItem> treeItems = new List<TreeItem>
{
//添加模块1
new TreeItem() { Id = 1, ParentId = 0, Name = "测试模块1", Nodes = new List<TreeItem>() },
new TreeItem() { Id = 2, ParentId = 1, Name = "测试模块1下的第一个页面", Nodes = new List<TreeItem>() },
new TreeItem() { Id = 3, ParentId = 1, Name = "测试模块1下的第二个页面", Nodes = new List<TreeItem>() },
//添加模块1下更多级节点
new TreeItem() { Id = 4, ParentId = 1, Name = "有子节点的子节点", Nodes = new List<TreeItem>() },
new TreeItem() { Id = 5, ParentId = 4, Name = "测试模块1下的有子节点的子节点第一个页面", Nodes = new List<TreeItem>() },
//添加模块2
new TreeItem() { Id = 6, ParentId = 0, Name = "测试模块2", Nodes = new List<TreeItem>() },
new TreeItem() { Id = 7, ParentId = 6, Name = "测试模块2下的第一个页面", Nodes = new List<TreeItem>() },
new TreeItem() { Id = 8, ParentId = 6, Name = "测试模块2下的第二个页面", Nodes = new List<TreeItem>() }
};
return treeItems;
}
private void ExcuteLoadUserControl(object obj)
{
if (obj is TreeView treeview)
{
foreach (var item in Plugins)
{
if (item.Metadata.Name == (treeview.SelectedItem as TreeItem).Name)
{
if (TabItemTests.Where(x => x.Header.ToString() == item.Metadata.Name).Count() < 1)
{
TabItemTests.Add(new TabItem()
{
Header = item.Metadata.Name,
Content = item.Value,
});
}
return;
}
}
}
}最后有个关于MVVMLight的问题没解决
UserControl的ViewModel我也是统一用ViewModelLocator来管理，
但是在xaml里 ViewModel不能绑定到UserControl的DataContext，只能绑给次一级元素的DataContext
<UserControl.Resources>
<ResourceDictionary>
<vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />
</ResourceDictionary>
</UserControl.Resources>
<Grid DataContext="{Binding Main,Source={StaticResource Locator}}">
<TextBlock Text="{Binding TestText}"/>
</Grid>参考链接：
https://www.cnblogs.com/hippieZhou/p/9404043.html#4183303
感谢@hippieZhou园友的指导。
第一次写随笔，只是根据这个链接照打了一遍。：）
原文：https://www.cnblogs.com/hfms/p/10409403.html