使用LINQ:

IEnumerable<ModelError> allErrors = ModelState.Values.SelectMany(v => v.Errors);

使用字段名和错误消息获取错误

var errors = new List<ErrorDto>();
foreach (KeyValuePair<string, ModelStateEntry> kvp in context.ModelState)
{
    if (kvp.Value.Errors.Count > 0)
    {
        errors.Add(new ErrorDto()
        {
            FieldName = kvp.Key,
            ErrorMessage = string.Join(",", kvp.Value.Errors.Select(v => v.ErrorMessage))
        });
    }
}

误差模型

    public class ErrorDto
    {
        public string FieldName { get; set; }
        public string ErrorMessage { get; set; }
    }

在您的实现中，您缺少静态类，这应该是。

if (!ModelState.IsValid)
{
    var errors =  ModelStateErrorHandler.GetModelErrors(this.ModelState);
    return Json(new { errors });
}

而

if (!ModelState.IsValid)
{
    var errors = ModelState.GetModelErrors();
    return Json(new { errors });
}

为了以防有人需要它，我在我的项目中创建并使用下面的静态类

使用的例子:

if (!ModelState.IsValid)
{
    var errors = ModelState.GetModelErrors();
    return Json(new { errors });
}

Usings:

using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Mvc;
using WebGrease.Css.Extensions;

类:

public static class ModelStateErrorHandler
{
    /// <summary>
    /// Returns a Key/Value pair with all the errors in the model
    /// according to the data annotation properties.
    /// </summary>
    /// <param name="errDictionary"></param>
    /// <returns>
    /// Key: Name of the property
    /// Value: The error message returned from data annotation
    /// </returns>
    public static Dictionary<string, string> GetModelErrors(this ModelStateDictionary errDictionary)
    {
        var errors = new Dictionary<string, string>();
        errDictionary.Where(k => k.Value.Errors.Count > 0).ForEach(i =>
        {
            var er = string.Join(", ", i.Value.Errors.Select(e => e.ErrorMessage).ToArray());
            errors.Add(i.Key, er);
        });
        return errors;
    }

    public static string StringifyModelErrors(this ModelStateDictionary errDictionary)
    {
        var errorsBuilder = new StringBuilder();
        var errors = errDictionary.GetModelErrors();
        errors.ForEach(key => errorsBuilder.AppendFormat("{0}: {1} -", key.Key,key.Value));
        return errorsBuilder.ToString();
    }
}

仅仅输出错误消息本身对我来说是不够的，但是这样做达到了目的。

var modelQuery = (from kvp in ModelState
                  let field = kvp.Key
                  let state = kvp.Value
                  where state.Errors.Count > 0
                  let val = state.Value?.AttemptedValue ?? "[NULL]"

                  let errors = string.Join(";", state.Errors.Select(err => err.ErrorMessage))
                  select string.Format("{0}:[{1}] (ERRORS: {2})", field, val, errors));

Trace.WriteLine(string.Join(Environment.NewLine, modelQuery));

我可以用一点LINQ来做这个，

public static List<string> GetErrorListFromModelState
                                              (ModelStateDictionary modelState)
{
      var query = from state in modelState.Values
                  from error in state.Errors
                  select error.ErrorMessage;

      var errorList = query.ToList();
      return errorList;
}

上面的方法返回一个验证错误列表。

进一步阅读:

如何在ASP中读取ModelState中的所有错误。NET MVC