在asp.net mvc中，如何添加验证

public class MyViewModel
{
    [Required(ErrorMessage = "用户名不能为空")]
    public string Username { get; set; }

    [Required(ErrorMessage = "密码不能为空")]
    [StringLength(20, MinimumLength = 6, ErrorMessage = "密码长度必须在6到20个字符之间")]
    public string Password { get; set; }
}

@model MyViewModel

@using (Html.BeginForm())
{
    <div>
        @Html.LabelFor(m => m.Username)
        @Html.TextBoxFor(m => m.Username)
        @Html.ValidationMessageFor(m => m.Username)
    </div>

    <div>
        @Html.LabelFor(m => m.Password)
        @Html.PasswordFor(m => m.Password)
        @Html.ValidationMessageFor(m => m.Password)
    </div>

    <input type="submit" value="提交" />
}

[HttpPost]
public ActionResult MyAction(MyViewModel model)
{
    if (ModelState.IsValid)
    {
        // 验证通过，执行相应的操作
        return RedirectToAction("Success");
    }

    // 验证失败，重新显示视图
    return View(model);
}