传入 WebApi 方法的 ViewModel 为 null

Question

不知道为什么我会遇到这个问题。我以前做过，但查看以前的项目没有任何帮助。我确定我缺少配置或其他东西。

我在一个 WebForms 4.5 项目中有一个 ApiController，用于从数据存储区 (SQL Server CE 4.0) 检索和更新数据。

我已经定义了以下 POST 方法来处理向产品添加属性记录...

    [HttpPost]
    public void AddPropertyToProduct([FromBody]ProductPropertyViewModel prodProp)
    {
        Mapper.CreateMap<ProductPropertyViewModel, ProductProperty>();
        ProductProperty property = Mapper.Map<ProductProperty>(prodProp);

        ProductRepository.Instance.AddProperty(property.ProductId, property);
        ProductRepository.Instance.SaveChanges();
    }

ProductPropertyViewModel 参数是我使用的 ViewModel，而不是数据模型...

public class ProductPropertyViewModel
{
    public Int64 Id { get; set; }

    public Int64 ProductId { get; set; }

    public String PropertyName { get; set; }

    public String PropertyValue { get; set; }

    public String Comments { get; set; }

    public DateTime DateAdded { get; set; }

    public DateTime DateUpdated { get; set; }

}

调用服务的客户端脚本发送一个 JSON 字符串，该字符串与属性的 ViewModel 属性相匹配...

var addPropertyToProduct = function (propertyViewModel, productId, isAsync, fnSuccess, fnError) {

    var methodUrl = "/api/ProductPropertyAPI/AddPropertyToProduct/"
    var ret = null;
    //
    // Make sure that the ProductId is specified as part of the ViewModel
    propertyViewModel.ProductId = productId;
    //
    // make sure that the propertyViewModel is reduced to JSON for being passed to the server.
    // Example : {"Id": 0, "ProductId":5,"PropertyName":"Engine Size","PropertyValue":"300cc","Comments":"Some comment","DateAdded":"07/25/2013","DateUpdated":"07/25/2013"}
    var jsonData = ko.toJSON(propertyViewModel);
    $.ajax({
        type: "POST",
        data: jsonData,
        async: isAsync,
        contentType: 'application/json;charset=utf-8',
        url: methodUrl,
        success: function (data) {
            //#region console log
            var logMsg = "AJAX.ProductPropertyAPI.AddPropertyToProduct ( "+ JSON.stringify(jsonData) +" ): RESPONSE : " + JSON.stringify(data);
            console.log(logMsg);
            //#endregion
            if (typeof fnSuccess === 'function') {
                fnSuccess(data);
            }
            else {
                defaultSuccess(data);
            }
        },
        error: function (data) {

            if (typeof fnError === 'function') {
                fnError(data);
            }
            else {
                defaultError(data);
            }
        }
    });
}

我遇到的问题是，当请求发布到服务的 AddPropertyToProduct 方法时，prodProp 参数是 NULL 而不是 ViewModel 的实例。据我了解，WebAPI 知道将 JSON 数据映射到 ProductPropertyViewModel 对象。

我确信我在这里忽略了一些东西，但无法弄清楚它是什么。谁能看到我错过了什么？

谢谢， G

更新：添加 Fiddler 数据

这是我通过 Fiddler 发送的请求。

POST http://localhost:55556/api/ProductPropertyAPI/AddPropertyToProduct HTTP/1.1
User-Agent: Fiddler
Host: localhost:55556
ContentType: 'application/json;charset=utf-8'
Content-Length: 155

{"Id": 0, "ProductId":5,"PropertyName":"Engine Size","PropertyValue":"300cc","Comments":"Some comment","DateAdded":"07/25/2013","DateUpdated":"07/25/2013"}

更新：添加了来自 IE 开发者工具的 $.Ajax 请求标头

Key Value
Request POST http://localhost:55556/api/ProductPropertyAPI/AddPropertyToProduct/ HTTP/1.1
Accept  */*
Content-Type    application/json;charset=utf-8
X-Requested-With    XMLHttpRequest
Referer http://localhost:55556/Admin/ProductManager.aspx
Accept-Language en-US
Accept-Encoding gzip, deflate
User-Agent  Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
Host    localhost:55556
Content-Length  129
DNT 1
Proxy-Connection    Keep-Alive
Pragma  no-cache
Cookie  __atuvc=38%7C8; __AntiXsrfToken=63a0ede574be4aa9a19e153474320450; ASPSESSIONIDACBTCRRS=FDDPEJIBPDFEODAHOEMBOOFK; ASPSESSIONIDCABTDTRT=AANBPPFCEFOBMAEFMMPMMFLF; ASPSESSIONIDAAARDSRS=LODHOFGCLJILEEEHICHGLNLA; ASPSESSIONIDCCDTCSQT=NHOJPJGCOECNJBIDGGKIALFG; ASP.NET_SessionId=xh4xctv0mvq2zb454hkb1f3z

Answer 1

我只是将您的代码复制粘贴到新项目中，但它失败了。

"Message":"An error has occurred.",
"ExceptionMessage":"Object reference not set to an instance of an object.",
"ExceptionType":"System.NullReferenceException"

我假设您遇到了同样的错误。但是在我删除之后：

contentType: 'application/json;charset=utf-8',

成功了。

我的完整 ajax 请求：

// I used static jsonData because you're getting the correct values in 
// your fiddler so this is definitely not causing any issues
var jsonData = { "Id": 0, "ProductId": 5, "PropertyName": "Engine Size", "PropertyValue": "300cc", "Comments": "Some comment", "DateAdded": "07/25/2013", "DateUpdated": "07/25/2013" };
var methodUrl = "/api/test/AddPropertyToProduct/";
$.ajax({
    type: "POST",
    data: jsonData,
    //async: isAsync,
    //contentType: 'application/json;charset=utf-8',
    url: methodUrl,
    success: function (data) {
        console.log('Success: ', data);
    },
    error: function (data) {
        console.log('Error: ', data);
    }
});

我使用的动作方法：

[HttpPost]
public string AddPropertyToProduct(ProductPropertyViewModel prodProp)
{
    return prodProp.PropertyName;
}