将以下代码添加到Global.asax.cs（Global.asax.vb）文件中的Application_Start方法中。

 https://docs.devexpress.com/eXpressAppFramework/113456/task-based-help/miscellaneous-ui-customizations/how-to-adjust-the-size-and-style-of-pop-up-dialogs-asp-net

 

using DevExpress.ExpressApp.Web.Controls;
using System.Web.UI.WebControls;
//...
protected void Application_Start(object sender, EventArgs e) {
    XafPopupWindowControl.DefaultHeight = Unit.Percentage(50);
    XafPopupWindowControl.DefaultWidth = Unit.Percentage(60);
    XafPopupWindowControl.PopupTemplateType = PopupTemplateType.FindDialog;
    XafPopupWindowControl.ShowPopupMode = ShowPopupMode.Centered;
    //...
}