@Code{ private List RadioItems { get; set; } = new List { new SelectedItem("1", "北京") { Active = true }, new SelectedItem("2", "上海") }; private void OnRadioItemChanged(CheckboxState state, SelectedItem item) { RadioDropDownItems.Add(new SelectedItem($"{RadioDropDownItems.Count()}", $"城市 {RadioDropDownItems.Count()}")); StateHasChanged(); } private List RadioDropDownItems { get; set; } = new List { new SelectedItem("1", "北京") { Active = true }, new SelectedItem("2", "上海"), new SelectedItem("3", "广州") }; }