向Web Service C＃添加构造函数

Question

Im trying to add an constructor to my webservice, that looks like this:

public class ILotusNotesService : System.Web.Services.WebService
{
    List<Calendar> cal = new List<Calendar>();
    [WebMethod]
    public List<Calendar> GetAllCal(string room)
    {
        DateTime d_start = new DateTime(2012,1,3,12,30,0);
        DateTime d_end = new DateTime(2012, 1, 3, 13, 00, 0);
        Calendar c1 = new Calendar("Søren Steffensen", "Mødelokale 1", "Privat", d_start, d_end);
        DateTime d_start2 = new DateTime(2012, 1, 3, 13, 30, 0);
        DateTime d_end2 = new DateTime(2012, 1, 3, 14, 00, 0);
        Calendar c2 = new Calendar("Knud Olesen", "Mødelokale 1", "Privat", d_start2, d_end2);
        DateTime d_start3 = new DateTime(2012, 1, 3, 15, 30, 0);
        DateTime d_end3 = new DateTime(2012, 1, 3, 16, 00, 0);
        Calendar c3 = new Calendar("Morten Nielsen", "Mødelokale 1", "Miljø Politik", d_start3, d_end3);
        cal.Add(c1);
        cal.Add(c2);
        cal.Add(c3);
        return cal;
    }

And the constructor looks like this

[DataContract(Name = "Calendar")]
public class Calendar: System.Web.Services.WebService
{
    [DataMember(Name = "_meetingHolder")]
    public String _meetingHolder { get; set; }

    [DataMember(Name = "_meetingRoom")]
    public String _meetingRoom { get; set; }

    [DataMember(Name = "_status")]
    public String _status { get; set; }

    [DataMember(Name = "_startTime")]
    public DateTime _startTime { get; set; }

    [DataMember(Name = "_endTime")]
    public DateTime _endTime { get; set; }


    public Calendar(string meetingHolder, string MeetingRoom,string status, DateTime startTime, DateTime endTime)
    {
        this._meetingHolder = meetingHolder;
        this._meetingRoom = MeetingRoom;
        this._status = status;
        this._startTime = startTime;
        this._endTime = endTime;
    }
}

But i keep getting this error:

LotusNotesServiveLibrary.Calendar cannot be serialized because it does not have a default public constructor

Answer 1

When writing an object that can be serialized, you must provide a constructor that has no parameters (a default constructor ):

public Calendar()

The reason is that when the objects gets deserialized, the deserializer must have a default way of creating an instance of the object.

Answer 2

That requirement has to be satisified, and once you add a constructor that takes parameters the compiler will not longer generate the default parameterless constructor for you. You can do this:

public Calendar() {
}

But then your member variables won't be initialized. If you have default values you'd like to use for them, you can also do this:

public Calendar():this("meetingHolder", new MeetingRoom(), "status",
                       new DateTime(), new DateTime()) {
}

And you'll have to come up with reasonable default values. Here I've just put dummy placeholders.

Answer 3

It is because you have to have a constructor without any parameter. Create a constructor without a parameter and assign default values to your properties.

Answer 4

That is because you simply cannot do it that way. When you publish a web service, the client will send data according to your data contract to you, and the .NET Framework will take that data and populate your data contract class (the Calendar class) using the properties you expose.

First of all, your data contract should not inherit from the WebService class. Second, just provide the default parameter-less constructor, and it will all work itself out.