ModelStateDictionary不包含CopyTo的定义

Question

在ASP.NET核心RC 1(完整.NET框架)中，下面的代码为我工作：

using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNet.Mvc;
using Microsoft.AspNet.Mvc.Filters;
using Microsoft.AspNet.Mvc.ModelBinding;
using Newtonsoft.Json;

namespace MyProject.Classes.Filters.ModelState
{
    public class SetTempDataModelStateAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);

            var controller = filterContext.Controller as Controller;
            if (controller != null)
            {
                var modelState = controller.ViewData.ModelState;
                if (modelState != null)
                {
                    var dictionary = new KeyValuePair<string, ModelStateEntry>[modelState.Count];
                    modelState.CopyTo(dictionary, 0);
                    var listError = dictionary.ToDictionary(m => m.Key, m => m.Value.Errors.Select(s => s.ErrorMessage).FirstOrDefault(s => s != null));
                    controller.TempData["ModelState"] = JsonConvert.SerializeObject(listError);
                }
            }
        }
    }
}

但是，在ASP.NET Core1.0(完整.NET框架)中，会发生以下错误：

using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Newtonsoft.Json;

namespace MyProject.Models.ModelState
{
    public class SetTempDataModelStateAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);

            var controller = filterContext.Controller as Controller;
            if (controller != null)
            {
                var modelState = controller.ViewData.ModelState;
                if (modelState != null)
                {
                    var dictionary = new KeyValuePair<string, ModelStateEntry>[modelState.Count];
                    modelState.CopyTo(dictionary, 0);
                    modelState = dictionary.[0];
                    var listError = dictionary.ToDictionary(m => m.Key, m => m.Value.Errors.Select(s => s.ErrorMessage).FirstOrDefault(s => s != null));
                    controller.TempData["ModelState"] = JsonConvert.SerializeObject(listError);
                }
            }
        }
    }
}

'ModelStateDictionary‘不包含'CopyTo’的定义，也找不到接受'ModelStateDictionary‘类型的第一个参数的扩展方法'CopyTo’(您缺少使用指令还是程序集引用？)

也许我需要连接到ASP.NET核心RC 1中不需要的程序集的新引用？

Answer 1

ModelStateDictionary没有实现IDictionary<,>，因此它没有一个CopyTo方法。在您的情况下，您可以将代码替换为

var listErrorr = modelState.ToDictionary(
  m => m.Key, 
  m => m.Value.Errors
    .Select(s => s.ErrorMessage)
    .FirstOrDefault(s => s != null)
); 

这在功能上应该等同于您在原始代码段中所做的工作。