错误Asp.Net的Web API实现自定义模型绑定 [英] Error implementing a Custom Model Binder in Asp.Net Web API

问题描述

即时通讯坚持这个很奇怪的问题。结果
我有一个名为API控制器 AttendanceController 从 APIControllerFA 这是inturn从 ApiController 结果
这里是code

im stuck with this very strange problem.
i have an API Controller named AttendanceController derived from APIControllerFA which is inturn derived from ApiController
here is the code

public class AttendanceController : ApiControllerFA
    {
        public HttpResponseMessage PostAttendance([ModelBinder(typeof(AttendanceRegistrationModelBinder))]AttendanceRegistrationModel model)
        {
            //checking model state for errors
            //throw new Exception("Just to throw an error ");

            ...........

由于可以在PostAttendance方法我有一个自定义的 ModelBinder的命名可以看出 AttendenceRegistrationModelBinder ，也是它的$ C $ç结果

As can be seen on the PostAttendance method i have a custom ModelBinder named AttendenceRegistrationModelBinder for which this is the code

public class AttendanceRegistrationModelBinder :  DefaultModelBinder
    {

        protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor)
        {
            if (propertyDescriptor.Name == "formJson")
            {
                string val = bindingContext.ValueProvider.GetValue(propertyDescriptor.Name).AttemptedValue;
                dynamic jsonVal = JsonConvert.DeserializeObject(val);
                propertyDescriptor.SetValue(bindingContext.Model, jsonVal);
                return;
                //SetProperty(controllerContext, bindingContext,propertyDescriptor,jsonVal);
            }
            base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
        }


    }

但是当我尝试访问使用提琴手这个控制器。我得到一个错误说

but when i try to access this controller using the Fiddler. i get an error saying

Could not create a 'IModelBinder' from 'AttendanceRegistrationModelBinder'. Please ensure it derives from 'IModelBinder' and has a public parameterless constructor

我在做什么错在这里？

what am i doing wrong here?

推荐答案

您遇到的问题是，你正在使用的MVC模式粘结剂不是的WebAPI。它看起来像您从 System.Web.Mvc.DefaultModelBinder 导出它实现 System.Web.Mvc.IModelBinder 。

The issue you are having is that you are using the MVC model binder not the WebApi. It looks like you are deriving from System.Web.Mvc.DefaultModelBinder which implements System.Web.Mvc.IModelBinder.

要创建的WebAPI自定义模型绑定您需要执行 System.Web.Http.IModelBinder 。

To create a custom model binder for WebApi you need to implement System.Web.Http.IModelBinder.

采取的WebAPI例如可一看模型粘合剂在CompsiteModelBinder <一个href=\"http://aspnetwebstack.$c$cplex.com/SourceControl/changeset/view/f079d76e57b5#src%2fSystem.Web.Http%2fModelBinding%2fBinders%2fCompositeModelBinder.cs\">http://aspnetwebstack.$c$cplex.com/SourceControl/changeset/view/f079d76e57b5#src%2fSystem.Web.Http%2fModelBinding%2fBinders%2fCompositeModelBinder.cs.

Take a look at the model binders available in WebApi e.g. the CompsiteModelBinder http://aspnetwebstack.codeplex.com/SourceControl/changeset/view/f079d76e57b5#src%2fSystem.Web.Http%2fModelBinding%2fBinders%2fCompositeModelBinder.cs.

一些有用的资源<一个href=\"http://blogs.msdn.com/b/jmstall/archive/2012/05/11/webapi-parameter-binding-under-the-hood.aspx\">here和<一个href=\"http://blogs.msdn.com/b/jmstall/archive/2012/04/16/how-webapi-does-parameter-binding.aspx\">here.

您是否使用<一个考虑href=\"http://www.hanselman.com/blog/TinyHappyFeatures2ASPNETWebAPIInVisualStudio2012.aspx\">JToken为您的JSON表单字段这可能工作没有定制绑定。

Have you considered using a JToken for your Json form field this may work without a custom binder.

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