C＃使用泛型方法

Question

I would like to know how I can solve the following problem:

I have a generic Method which return response data.

public class Request
{
    public T PostRequest<T>(string Ressource, T ObjTOPost) where T : new()
    {
        var request = new RestRequest(Ressource, Method.POST);

        var client = new RestClient("https://api.net/api/v1/");

        request.XmlSerializer = new RestSharp.Serializers.XmlSerializer();
        request.RequestFormat = DataFormat.Xml;

        request.AddXmlBody(ObjTOPost, "http://api.net");
        var response = client.Execute<T>(request);

        return response.Data;
    }
}

When I call the Method like this it says that LoginXML cannot be converted to UserXML. I dont get why because LoginXML is a parameter only for serializing my properties for the post request.

var login = new LoginXML();
        login.username = tbUsername.Text;
        login.password = tbPassword.Text;

Request req = new Request();
UserXML user = req.PostRequest("sessions", login);

Here are my LoginXML and UserXML

 [SerializeAs(Name = "login")]
public class LoginXML
{
    private string user;
    private string pw;
    private string ID;

    [DeserializeAs(Name = "id")]
    public string sessionID { get; set; }
    [SerializeAs(Name = "username")]
    public string username
    {
        get
        {
            return this.user;
        }
        set
        {
            this.user = value.Trim();
        }
    }
    [SerializeAs(Name = "password")]
    public string password
    {
        get { return this.pw; }
        set { this.pw = value.Trim(); }
    }
}

public class UserXML
{
    private string ID;

    [DeserializeAs(Name = "id")]
    public string sessionID {get;set;}
}

Answer 1

public T PostRequest<T>(string Ressource, T ObjTOPost) where T : new()

Your PostRequest return type is T , which is similar to T ObjTOPost . Since you passed in a LoginXML instance into req.PostRequest("sessions", login); it'd assume your return type will also be LoginXML since they are both T.

public T PostRequest<T>(string Ressource, T ObjTOPost) where T : new()
{
    // Some code
    return response.Data;
}

Here you are trying to return the Data retrieved from your rest request which is a UserXML type. However in this case your method return type is LoginXML but you are returning a UserXML object instead, hence the error.

One way is to simply return object but it requires the trouble of casting every object and there will be potentially bad casts that causes exceptions.