revit开发一个插件，创建一个嵌套族，给出完整代码

Revit API提供了一个强大的框架来开发自定义插件，包括创建嵌套族的功能。在Revit中，嵌套族（Nested Family）是指可以在另一个族中使用的子族。以下是一个简单的例子，展示了如何使用C#编写一个基础的Revit插件来创建嵌套族：

using Autodesk.Revit.DB;
using Autodesk.Revit.UI;

[Transaction(TransactionMode.ReadOnly)]
public class CreateNestedFamily : IExternalCommand
{
    public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
    {
        try
        {
            // 获取当前项目
            Document doc = commandData.Application.ActiveUIDocument.Document;

            // 创建新的嵌套族类型
            FamilyType parentType = doc.GetElement(commandData.InputParameters[0].AsElementId()).AsFamilyType();
            Family newNestedType = doc.FamilyCreate.NewFamilyType(parentType);

            // 添加族参数
            FamilyParameter param = new NestedParamDefinition(newNestedType);
            newNestedType.Parameters.Add(param);

            // 创建嵌套族实例
            FamilyInstance nestedInstance = newNestedType.CreateNewInstance(doc);

            // 将嵌套族添加到父族中
            parentType.GetNestedFamilyTypes().Add(nestedInstance.GetType());

            message = "Nested family created successfully.";
            return Result.Succeeded;
        }
        catch (Exception ex)
        {
            message = $"Error: {ex.Message}";
            return Result.Failed;
        }
    }

    private FamilyParameter NestedParamDefinition(FamilyType type)
    {
        // 这里只是一个简单的参数定义示例，你可以根据需要设置参数类型、名称等
        BuiltInParameter categoryParam = BuiltInParameter.PROJECT_NAME_PARAM;
        Category defaultCategory = Category.GetCategory(doc, BuiltInCategory.OST_GenericModel);
        return type.AddParameter("Nested Param", "A parameter for the nested family.", categoryParam, defaultCategory);
    }
}

// 插件注册
[Autodesk.Revit.UI.AddInRegistration]
class AddInRegistration
{
    [Autodesk.Revit.UI.AddInMenu("Custom Menu", "My Tools")]
    public static readonly CommandId MyCommandId = new CommandId(Guid.Parse("YOUR_ADDIN_GUID"), 1001); // Replace with your addin's GUID

    [Autodesk.Revit.UI.Dockable(true)]
    public static readonly DockPanelType MyDockPanelType = DockPanelType.Unknown;

    [Autodesk.Revit.UI.Transaction]
    public static void Initialize()
    {
        CommandFactory factory = new CommandFactory();
        factory.Name = "Create Nested Family";
        factory.Id = MyCommandId;
        factory.DocumentFilter = DocumentFilterUtils.AllDocuments;
        factory.ExecuteMethod = delegate (ExternalCommandData commandData) => new CreateNestedFamily().Execute(commandData, out _, default(ElementSet));
    }
}

在这个例子中，你需要替换`YOUR_ADDIN_GUID`为你的插件的实际GUID。此外，`NestedParamDefinition`函数可以根据需求定制嵌套家族的参数。