ASP.NET MVC 顯示 UserControl 進階：AscxUtility 封裝與 Action 重構

將渲染 UserControl 邏輯封裝為 AscxUtility 靜態類別，支援泛型與多載，可在 Action 與 Razor 視圖中直接呼叫。

AscxUtility 核心方法

public static HtmlString RenderControl<T>(string path) where T : UserControl {
    var page = new Page();
    var control = (T)page.LoadControl(path);
    page.Controls.Add(control);
    var writer = new StringWriter();
    var htmlWriter = new HtmlTextWriter(writer);
    page.RenderControl(htmlWriter);
    return new HtmlString(writer.ToString());
}

Controller 簡化

public ActionResult UcTest() {
    return Content(AscxUtility.RenderControl<WebUserControl1>("~/AspNets/WebUserControl1.ascx").ToString());
}

進一步支援視圖直接呼叫：@AscxUtility.RenderControl<WebUserControl1>("~/AspNets/WebUserControl1.ascx")，實現邏輯複用與關注點分離。