如何将ViewDataDictionary或ModelStateDictionary注入TagHelper？

Question

在剃刀视图中,我可以访问模型状态对象:

@ViewData.ModelState

我如何在剃须刀中注射和访问ViewData或ModelState对象TagHelper？我尝试了以下,但是ViewData并且ModelState始终为null:

public class ModelStateTagHelper : TagHelper
{
    public ViewDataDictionary ViewData { get; set; }
    public ModelStateDictionary ModelState { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
    }
}

Answer 1

对于那些寻找ViewData而不是那些的人ModelState,你可以添加ViewContext到你的TagHelper.

public class EmailTagHelper : TagHelper
{
    [ViewContext]
    public ViewContext ViewContext { get; set; }

    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        var hasACertainKey = this.ViewContext.ViewData.ContainsKey("ACertainKey");
    }
}

Answer 2

您可以注入IActionContextAccessor：

    public void ConfigureServices(IServiceCollection services)
    {
        //...
        services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
    }

    public class ModelStateTagHelper : TagHelper
    {
        public readonly IActionContextAccessor _accessor;

        public ModelStateTagHelper(IActionContextAccessor accessor)
        {
            _accessor = accessor;
        }
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var modelState = _accessor.ActionContext.ModelState;
        }
    }