WCF DataMember not available or visible in Client what am I doing wrong?

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I cannot see the DataMember .. datas belonging to the DataService class from my winforms WCF Client, I can do the operations and that works fine - I just cannot see this DataMember object {datas} ; what am I doing wrong?

Below is the example code:

C#

    [DataContract]
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
    public class DataService : IDataService  
    {   // have tried this too [DataMember] on backing field. 	
        BindingList<Data> m_datas;        
        [DataMember]
	public BindingList<Data> datas 
	{
		get 
		{
		  if (this.m_datas == null) 
		  {
		     this.m_datas = new BindingList<Data>();
		  }
		    return this.m_datas;
		}
		set 
		{
		   m_datas = value;
		}
	}
}

My interface is

C#

[ServiceContract]
public interface IDataService
{
	[OperationContract]
	BindingList<Data> GetData();
}

[DataContract]
public class Data
{
   [DataMember]
   public string name;
}

The reason I want to do this; is that I have a service that is constantly running and monitoring - it then updates this internal list of objects, which I then want my client to show real time updates - I can show the data by using GetData but this requires me to handle this all the time whenever the list changes in the service. Isn't there a better way to do this ?

Posted 27-May-15 11:45am

stixoffire

Updated 28-May-15 6:26am

v3

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Comments

macika123 27-May-15 18:11pm

Did you mark class Data also as DataContract and its members as DataMember like you did with DataService?

stixoffire 28-May-15 9:43am

I added the class to the question, yes it is marked and for the life of me I am stumped as to why it is not there - I updated the reference as well - and it is still not showing up.

Mathi Mani 27-May-15 19:27pm

Implementation seems wrong. Why are you marking Service implementation as [DataContract]?

stixoffire 28-May-15 9:35am

I am trying to get the BindingList to show up in my client app, and so I marked it thinking I will see if the problem is between the chair and the code.

stixoffire 28-May-15 12:20pm

OK so MSDN says I cannot have a DataMember in the service contract thanks for that hint that I am doing something wrong. Now I need to know how to reflect changes of this binding list back to my client - I was preferring not to do GetData repetitively. So I will need to know when that list changes and create a method to trigger an update of the client - I do not know how to have the WCF service update this object in a Winform automagically - unless I need to reference the application.MyObjectList some how to do this.

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Shmuel Zang · Accepted Answer · 2015-05-27T20:12:00

Solution 1

Where do you want to access the datas property of your service? Does it in the client side? If so, It looks like there is a little misunderstanding of how the things works.

When you create a client to your service (using ChannelFactory or Add Service Reference), it creates an object that implements your ServiceContract (in your case: IDataService) and contains implementation for your OperationContracts - No properties are transfered.

If you want to get the value of datas, you should implement GetData to return it. You should declare the data (Data) as a DataContract (not the service...)

Posted 27-May-15 20:12pm

Shmuel Zang

Comments

stixoffire 28-May-15 9:47am

If I use GetData - then I physically need to request it when a change is made to the underlying component. I have a DataGridView that is bound to a datasource (which I do use GetData to fill that bindingsource - but when I add to this Datas - it is there but I do not get the changes reflected back in my DataGridView - so I am trying to bind my bindingsource to this component directly for the changes to be reflected in my client. Am I going about this wrong ?

stixoffire 28-May-15 12:56pm

Maybe there is no way to do what I would like to do except to use a listchanged event in the service and trigger a WCFCallback that my Client can receive ??? Is that how I need to do this ? I have things working with GetData() but when the "datas" changes I want my Client DataGridView to reflect those changes in close proximity to real time - <200ms or so .

Shmuel Zang 28-May-15 14:42pm

Sending callback to the client can be a good idea. See also about: WCF Duplex Services.

stixoffire 28-May-15 15:15pm

I was expecting something similar to the bindingsource data changes - the DataGridView automagic update by binding to that list, As I have been reading WCF does not work so nice like that. II really do not want to get the whole datasource to send , but only changes so maybe I need to know what indexes in the list changed and send them on the callback and in the receive handle the changedevent . So then I need a better collection object where I can know what items are changed, added, modified , new - and I am thinking a DataTable would have all of that built in , so I do not need to roll my own stuff. Any thoughts as to if this is a good or bad idea ?

stixoffire 30-May-15 6:57am

Is there a difference between duplex services and using callbacks? - they seem to be the same to me, and the example at the link is what I have implemented to test out. What is WCF Data services used for - does it do anything special for me that Duplex Services can't ?