如何将ViewDataDictionary或ModelStateDictionary注入到TagHelper中？

Question

在剃刀视图中，我可以访问模型状态对象：

@ViewData.ModelState

如何在razor TagHelper中注入和访问ViewData或ModelState对象？我尝试了以下方法，但ViewData和ModelState始终为空：

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

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

Answer 1

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;
        }
    }

Answer 2

对于那些寻找ViewData而不是ModelState的用户，可以将ViewContext添加到您的TagHelper中。

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");
    }
}