c#没有为DTO属性中的类型定义无参数构造函数

Question

I have a question I have a simple operation that is using RestClient to get info, and code looks like:

 var client = new RestClient(RestClientBaseUrl);
 IRestResponse request = client.Execute(new RestRequest("Application/GetApplications", Method.GET));
 IEnumerable<DTO.Application> response = new JsonDeserializer().Deserialize<IEnumerable<DTO.Application>>(request);

DTO for this model looks like:

public class Application
{
    public int? Id { get; set; }
    public string Name { get; set; }
    public GetSystem[] Systems { get; set; }
}

and for system it looks like:

public class GetSystem : SystemTemplate
{
    public int Id { get; set; }
    public SystemState SystemState { get; set; }
}

System template

public abstract class SystemTemplate
{
    public string Name { get; set; }
    public string IpAddress { get; set; }
    public int Port { get; set; }
}

and SystemState:

public class SystemState
{
    public int? Id { get; set; }
    public byte MaintenanceMode { get; set; }
    public string LastCommunicationTimestamp { get; set; }
    public int SystemId { get; set; }
}

Now problem is when I deserialize Json I am getting:

System.MissingMethodException : No parameterless constructor defined for type 'DS.Models.DTO.GetSystem[]'.

What could be the problem?

Answer 1

您需要在 GetSystem 类中添加一个空的构造函数。

Answer 2

During deserialization JsonDeserializer needs to create the object first and then populates it with data. It will use the default parameterless contrusctor for that. It obviously cannot create the object. Check, that you can actually create your object, ie:

GetSystem getSystem = new GetSystem();

The GetSystem seems to be ok, so the problem must be in the base class SystemTemplate or some other base class you didn't post. You will need to add the parameterless constructor and make it accessible to the calling class. Make sure it is not private.