任何人在寻找asp.net core 3.1。比上面的答案略有更新。我发现这就是[ApiController]返回的内容

 Dictionary<string, List<string>> errors = new Dictionary<string, List<string>>();

                foreach (KeyValuePair<string, ModelStateEntry> kvp in ViewData.ModelState)
                {
                    string key = kvp.Key;
                    ModelStateEntry entry = kvp.Value;

                    if (entry.Errors.Count > 0)
                    {
                        List<string> errorList = new List<string>();
                        foreach (ModelError error in entry.Errors)
                        {
                            errorList.Add(error.ErrorMessage);
                        }

                        errors[key] = errorList;
                    }
                }

                return  new JsonResult(new {Errors = errors});

任何人在寻找asp.net core 3.1。比上面的答案略有更新。我发现这就是[ApiController]返回的内容

 Dictionary<string, List<string>> errors = new Dictionary<string, List<string>>();

                foreach (KeyValuePair<string, ModelStateEntry> kvp in ViewData.ModelState)
                {
                    string key = kvp.Key;
                    ModelStateEntry entry = kvp.Value;

                    if (entry.Errors.Count > 0)
                    {
                        List<string> errorList = new List<string>();
                        foreach (ModelError error in entry.Errors)
                        {
                            errorList.Add(error.ErrorMessage);
                        }

                        errors[key] = errorList;
                    }
                }

                return  new JsonResult(new {Errors = errors});

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));

var result = string.Join('，'，ModelState.Values。SelectMany(v => . errors).Select(a=> . errormessage));

基于LINQ版本，如果你想将所有错误消息连接到一个字符串中:

string messages = string.Join("; ", ModelState.Values
                                        .SelectMany(x => x.Errors)
                                        .Select(x => x.ErrorMessage));

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; }
    }