在自定义模型绑定器中设置ModelState值

Question

我在ASP.NET MVC 2中使用自定义模型绑定器,如下所示:

    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        if (controllerContext == null)
        {
            throw new ArgumentNullException("controllerContext");
        }
        if (bindingContext == null)
        {
            throw new ArgumentNullException("bindingContext");
        }

        BaseContentObject obj = (BaseContentObject)base.BindModel(controllerContext, bindingContext);
        if(string.IsNullOrWhiteSpace(obj.Slug))
        {
            // creating new object
            obj.Created = obj.Modified = DateTime.Now;
            obj.ModifiedBy = obj.CreatedBy = controllerContext.HttpContext.User.Identity.Name;
            // slug is not provided thru UI, derivate it from Title; property setter removes chars that are not allowed
            obj.Slug = obj.Title;
            ModelStateDictionary modelStateDictionary = bindingContext.ModelState;
            modelStateDictionary.SetModelValue("Slug", new ValueProviderResult(obj.Slug, obj.Slug, null));
...

当我从这个绑定器返回到控制器操作时,我作为操作参数提供的业务对象被正确更改(行obj.Created = .... work).

但是,ModelState不会更新.我知道这是因为我在业务对象的Slug属性上有必需,虽然我在我的自定义模型绑定器中修改了ModelStateDictionary,为它提供了一个Slug(如上所示),但ModelState.IsValid仍然是假的.

如果我在调试会话中的Watch窗口中放置了ModelState ["Slug"],它说它有错误(1),所以显然它是空的,因此失败了.

如何在自定义模型绑定器代码中正确更改ModelState？

Answer 1

显然,一旦更改了某个键的值,就无法重新验证ModelState.IsValid仍然为false,因为为某个键设置新值不会触发重新验证.

解决方案是首先删除触发IsValid为false的密钥并重新创建它并为其分配值.当你这样做时,ModelState会自动重新生效,如果一切正常,则IsValid返回true.

像这样:

bindingContext.ModelState.Remove("Slug");
bindingContext.ModelState.Add("Slug", new ModelState());
bindingContext.ModelState.SetModelValue("Slug", new ValueProviderResult(obj.Slug, obj.Slug, null));