在Asp.net核心Mvc中提交表单后，下拉列表不保留选定的值

// POST方法中获取选定的值并传递到视图页面
[HttpPost]
public IActionResult SubmitForm(string selectedValue)
{
    ViewBag.SelectedValue = selectedValue;
    return View();
}

<select>
    <option value="value1" @(ViewBag.SelectedValue == "value1" ? "selected" : "")>Option 1</option>
    <option value="value2" @(ViewBag.SelectedValue == "value2" ? "selected" : "")>Option 2</option>
    <!-- 其他选项 -->
</select>

// 模型类
public class MyModel
{
    public string SelectedValue { get; set; }
    // 其他表单字段
}

// GET方法返回带有选定的值的视图页面
[HttpGet]
public IActionResult SubmitForm()
{
    MyModel model = new MyModel();
    model.SelectedValue = "value1"; // 设置选定的值
    return View(model);
}

// POST方法中获取选定的值并传递到视图页面
[HttpPost]
public IActionResult SubmitForm(MyModel model)
{
    model.SelectedValue = model.SelectedValue; // 重新获取选定的值
    return View(model);
}

<select>
    <option value="value1" @(Model.SelectedValue == "value1" ? "selected" : "")>Option 1</option>
    <option value="value2" @(Model.SelectedValue == "value2" ? "selected" : "")>Option 2</option>
    <!-- 其他选项 -->
</select>