在Web API中调用PUT方法时出现以下错误？ [英] Getting following error while calling the PUT method in web API?

问题描述

 1]参数字典包含方法'System.Net.Http.HttpResponseMessage Put（Int32，ClassLibrary2.Employee）的非可空类型'System.Int32'的参数'id'的空条目''在'EmployeeService.Controllers.EmployeeController'中。可选参数必须是引用类型，可空类型，或者声明为可选参数。 
 
 2]第二次错误我的ID值为0 
 
请参阅以下COde： -  

我尝试过：

 public HttpResponseMessage Put（[FromBody] int id， [FromUri]员工员工）
 {
 try 
 {
 using（EmployeeDBEntities entities = new EmployeeDBEntities（））
 {
 var entity = entities.Employees .FirstOrDefault（e => e.ID == id）; 
 if（entity == null）
 {
返回Request.CreateErrorResponse（HttpStatusCode.NotFound，
带有Id的员工+ id.ToString（）+未找到更新）; 
} 
 else 
 {
 entity.FirstName = employee.FirstName; 
 entity.LastName = employee.LastName; 
 entity.Gender = employee.Gender; 
 entity.Salary = employee.Salary; 
 
 entities.SaveChanges（）; 
 
返回Request.CreateResponse（HttpStatusCode.OK，entity）; 
} 
} 
} 
 catch（Exception ex）
 {
返回Request.CreateErrorResponse（HttpStatusCode.BadRequest，ex）; 
} 
} 

请查找WebApiConfig.Cs文件： - < br $>

 public static void Register（HttpConfiguration config）
 {
 // Web API配置和服务
 
 // Web API路由
 config.MapHttpAttributeRoutes（）; 
 
 config.Routes.MapHttpRoute（
 name：DefaultApi，
 routeTemplate：api / {controller} / {id}，
 defaults：new { id = RouteParameter.Optional} 
）; 
 
 config.Formatters.JsonFormatter.SerializerSettings.Formatting = Newtonsoft.Json.Formatting.Indented; 
 config.Formatters.JsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver（）; 
} 

解决方案

您的Put命令是什么样的？

错误正在尝试告诉你你没有在它认为匹配id参数的Put命令中发送的值。

[FromBody]属性意味着它正在寻找发布数据正文中的数据（不在参数字符串中？id = 77或其他）。

在WebAPI方法上，将属性从[FromBody]更改为[FromUri]。

< pre lang =c＃> [FromUri（）] int id

1]The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'System.Net.Http.HttpResponseMessage Put(Int32, ClassLibrary2.Employee)' in 'EmployeeService.Controllers.EmployeeController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.

2]Second Error I am getting ID values as 0

Please refer Following COde:-

What I have tried:

public HttpResponseMessage Put([FromBody]int id, [FromUri]Employee employee)
        {
            try
            {
                using (EmployeeDBEntities entities = new EmployeeDBEntities())
                {
                    var entity = entities.Employees.FirstOrDefault(e => e.ID == id);
                    if (entity == null)
                    {
                        return Request.CreateErrorResponse(HttpStatusCode.NotFound,
                            "Employee with Id " + id.ToString() + " not found to update");
                    }
                    else
                    {
                        entity.FirstName = employee.FirstName;
                        entity.LastName = employee.LastName;
                        entity.Gender = employee.Gender;
                        entity.Salary = employee.Salary;

                        entities.SaveChanges();

                        return Request.CreateResponse(HttpStatusCode.OK, entity);
                    }
                }
            }
            catch (Exception ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
            }
        }

Please Find WebApiConfig.Cs file:-

public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );

            config.Formatters.JsonFormatter.SerializerSettings.Formatting = Newtonsoft.Json.Formatting.Indented;
            config.Formatters.JsonFormatter.SerializerSettings.ContractResolver= new CamelCasePropertyNamesContractResolver();
        }

解决方案

What does your Put command look like?
The error is trying to tell you that you don't have a value sent in on the Put command that it thinks matches the id parameter.
The [FromBody] attribute means it's looking for the data in the body of the posted data (not in the parameter string ?id=77 or whatever).

On your WebAPI method change the attribute from [FromBody] to [FromUri].

[FromUri()] int id

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