异常消息 ": " 没有媒体类型格式化程序可用于从媒体类型为"多部分/表单数据"的内容中读取类型为"用户"的对象"postman"

Question

我正在使用Web API创建登录服务。当我检查fiddler时它工作正常，但当我检查chrome的postman时，它显示错误:

{    "Message": "An error has occurred.",
    "ExceptionMessage": "No MediaTypeFormatter is available to read an object of type 'user' from content with media type 'multipart/form-data'.",
    "ExceptionType": "System.InvalidOperationException",
    "StackTrace": "   
    at System.Net.Http.HttpContentExtensions.ReadAsAsync[T](HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger)rn
    at System.Net.Http.HttpContentExtensions.ReadAsAsync(HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger)rn
    at System.Web.Http.ModelBinding.FormatterParameterBinding.ReadContentAsync(HttpRequestMessage request, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger)rn
    at System.Web.Http.ModelBinding.FormatterParameterBinding.ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken)rn
    at System.Web.Http.Controllers.HttpActionBinding.<>c__DisplayClass1.<ExecuteBindingAsync>b__0(HttpParameterBinding parameterBinder)rn
    at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()rn
    at System.Threading.Tasks.TaskHelpers.IterateImpl(IEnumerator`1 enumerator, CancellationToken cancellationToken)" 
}

public class user
{
    //public user(string userId, string password)
    //{
    //    UserId = userId;
    //    Password = password;
    //}
    public string UserId { get; set; }
    public string Password { get; set; }
}

我正在检查postman，如果这项服务能够在移动应用程序中访问。另外，要在mac系统中检查这个

Answer 1

点击Header按钮，键入Header和value

Content-Type: application/json

检查下面的链接，小提琴和邮差都使用相同的内容类型在POST中向web API服务发送json错误

Answer 2

我遇到了同样的问题，但后来我发现我正在调用WebAPI使用ajax POST，我把它改为GET，它工作了。但错误大多是误导。所以我一直专注于媒体类型。

请求实体的媒体类型'text/plain'不支持此资源"，

$http({             
method: 'POST',

改为

$http({             
method: '**GET**',