Ajax调用MVC操作方法-没有为此对象定义无参数构造函数

Question

I'm making the following AJAX call to an action method in an ASP.NET MVC controller:

    $.ajax({
        type: 'POST',
        contentType: "application/json; charset=utf-8",
        url: appControllerUrl + "/SaveAppDetails",
        data: {appDetails: JSON.stringify(appDetailsView.model)},
        processData: true,
        dataType: "json"
    });

However I get an HTTP 500 error stating 'No parameterless constructor defined for this object'. Here is my controller:

public class AppDetailsController
{
    // GET: AppDetails
    AppDetailsController() { }

    [HttpPost]
    public ActionResult SaveAppDetails(string appDetails)
    {
       ...
    }

The 'data' that the Ajax call passes to the controller looks this this:

appDetails= {"id":{"type":"string"},"appName":{"type":"string"},"guid":21}

... so it looks like the actual data I need isn't being passed, however the data string itself seems to be well formed. What's causing the error?

Answer 1

The error means that MVC is trying to instantiate a controller but cannot do so. In C#, if you declare a constructor and don't specify an accessibility modifier, it will be private . You should add the public modifier to the constructor of AppDetailsController .

Answer 2

Javascript Example

appDetailsView.model = {
         Id: $.trim(idExample),
         AppName: $.trim(appNameExample),
         Guid: 21
      };

Ajax

$.ajax({
        type: 'POST',
        contentType: "application/json; charset=utf-8",
        url: appControllerUrl + "/SaveAppDetails",
        data: JSON.stringify(appDetailsView.model),
        processData: true,
        dataType: "json"
    });

Action

public class AppDetailsController
{
    // GET: AppDetails
    public AppDetailsController() { }

    [HttpPost]
    public ActionResult SaveAppDetails(AppDetailsView appDetails)
    {
       ...
    }

Class View Model

public class AppDetailsView{
     public string Id { get; set; }
     public string AppName { get; set; }
     public int Guid { get; set; }
}