//============代碼片段2-1：外部命令中Excute函數的定義============
public?interface?IExternalCommand
{
??public?Autodesk.Revit.UI.Result?Execute（
???Autodesk.Revit.UI.ExternalCommandData?commandData
???ref?string?message
???Autodesk.Revit.DB.ElementSet?elements）
}

//============代碼片段2-2：從commandData中取到Document============
UIApplication?uiApplication?=?commandData.Application;
Application?application?=?uiApplication.Application;
UIDocument?uiDocument?=?uiApplication.ActiveUIDocument;
Document?document?=?uiDocument.Document;

//============代碼片段2-3：使用message參數============
???public?class?command?:?IExternalCommand
???{
??????public?Result?Execute（
?????????????ExternalCommandData?commandData
?????????????ref?string?message
?????????????ElementSet?elements）
??????{
?????????message?=?“message?test“;
?????????return?Result.Failed;
??????}
???}

//============代碼片段2-4：使用element參數============
public?Result?Execute（ExternalCommandData?commandData?ref?string?message?ElementSet?elements）
{
???message?=?“Please?take?attention?on?the?highlighted?Walls!“;
???//先從UI選取元素，然后執行該插件
???ElementSet?elems?=?commandData.Application.ActiveUIDocument.Selection.Elements;
???foreach?（Element?elem?in?elems）
???{
??????Wall?wall?=?elem?as?Wall;
??????if?（null?!=?wall）
??????{
???elements.Insert（elem）;
??????}
???}
???return?Result.Failed;
}

//============代碼片段2-5：外部命令中Excute函數的返回值============
public?Result?Execute（ExternalCommandData?commandData?ref?string?message?ElementSet?elements）
{
???try
???{
??????UIDocument?uiDoc?=?commandData.Application.ActiveUIDocument;
??????Document?doc?=?uiDoc.Document;
??????List?selectedElem?=?new?List（）;
??????foreach（Element?elem?in?uiDoc.Selection.Elements）
??????{
?????????selectedElem.Add（elem.Id）;
??????}

??????doc.Delete（selectedElem）;

??????TaskDialogResult?result?=?TaskDialog.Show（
?????????“Revit“
?????????“Yes?to?return?succeeded?and?delete?all?selection“+
?????????“No?to?cancel?all?commands.“
?????????TaskDialogCommonButtons.Yes|TaskDialogCommonButtons.No）;

??????if?（TaskDialogResult.Yes?==?result）
??????{
?????????return?Result.Succeeded;
??????}
??????else?if?（TaskDialogResult.No?==?result）
??????{
?????????elements?=?uiDoc.Selection.Elements;
?????????message?=?“Failed?to?delete?selection.“;
?????????return?Result.Failed;
??????}
??????else
??????{
?????????return?Result.Cancelled;
??????}
???}
???catch
???{
??????message?=?“Unexpected?Exception?is?thrown?out.“;
??????return?Result.Failed;
???}
}

//============代碼片段2-6：IExternalApplication接口定義============
public?interface?IExternalApplication
{
???Autodesk.Revit.UI.Result?OnShutdown（UIControlledApplication?application）;
???Autodesk.Revit.UI.Result?onstartup（UIControlledApplication?application）;
}

//============代碼片段2-7：使用IExternalApplication定制UI============
public?Autodesk.Revit.UI.Result?onstartup（UIControlledApplication?application）
{
???//添加一個新的Ribbon面板
???RibbonPanel?ribbonPanel?=?application.CreateRibbonPanel（“NewRibbonPanel“）;

???//在新的Ribbon面板上添加一個按鈕
?