对于AJAX请求更好的解决方案:

    public IActionResult Demo(DemoInfo formData)
    {
        if (!ModelState.IsValid)
        {
            IEnumerable<object> formErrors = ModelState.Select((s) => new { 
                fieldName = s.Key, 
                fieldValue = s.Value.RawValue,
                fieldMessage = s.Value.Errors.FirstOrDefault()?.ErrorMessage
            });
            return Json(new { formValid = 0, formErrors });
        }
        return Json(new { formValid = 1 });
    }

回应格式为:

{"formValid":0,
 "formErrors":[{
     "fieldName":"name of field from object",
     "fieldValue":"value from browser",
     "fieldMessage":null /*Error message from model annotations if field is valid the value will be null */
 }]
}

有关Func<>的更多详细信息，请查看本页:Func<TSource,Int32,TResult>)

foreach (ModelState modelState in ViewData.ModelState.Values) {
    foreach (ModelError error in modelState.Errors) {
        DoSomethingWith(error);
    }
}

请参见如何在ASP中获取模型状态错误的集合。净MVC ?。

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));

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 });
}

使用LINQ:

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

var x = new Dictionary<string,string>();
for (var b = 0; b < ViewData.ModelState.Values.Count(); b++)
{
    if (ViewData.ModelState.Values.ElementAt(b).Errors.Count() > 0)
        x.Add(ViewData.ModelState.Keys.ElementAt(b), String.Join(",", ViewData
            .ModelState.Values.ElementAt(b).Errors.Select(c => c.ErrorMessage)));
}