Revit二次开发---未打开项目使用面板功能

1.创建面板按钮时需要设置“AvailabilityClassName”

2.需额外实现 “IExternalCommandAvailability” 接口

//
PushButtonData item1 = new PushButtonData("test", "测试", dllPath, "Test.cmdTest");
item1.AvailabilityClassName = "Test.cmdTest";

//
    [Transaction(TransactionMode.Manual)]
    public class cmdTest : IExternalCommand, IExternalCommandAvailability
    {
        public Autodesk.Revit.UI.Result Execute(Autodesk.Revit.UI.ExternalCommandData revit, ref string message,Autodesk.Revit.DB.ElementSet elements)
        {
            return Result.Succeeded;
        }
        public bool IsCommandAvailable(UIApplication applicationData, CategorySet selectedCategories)
        {
            return true;
        }

    }