Question

I have created a simple service to provide configuration options as a Dictionary. I created a new SerializableDictionary class that implements IXmlSerializable as described on this board. When I add the service (via “Add Service Reference” in my consumer project), the method signature shows that it returns a DataSet. When I examine the DataSet at runtime it is empty.

Here is my service:

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
// [System.Web.Script.Services.ScriptService]
public class AppSettingsService : System.Web.Services.WebService
{
        [WebMethod]
        public SerializableDictionary<string, string> ReadAppSettings()
        {
            return AppSettings.Settings; // Settings is a SerializableDictionary<string, string>
        }
}

On the Client side I do this:

using Clients.AppSettingsServiceReference;

        static AppSettings()
        {
            AppSettingsServiceSoapClient client = new AppSettingsServiceSoapClient();
            var settings = client.ReadAppSettings();
            // ...
        }

I expect settings to be a SerializableDictionary but it’s an empty DataSet. I’ve tried sending it as a List of KeyValuePairs as suggested here and elsewhere but that also returns a DataSet. I’m using C#, ASP.Net 3.5, VS2008 Pro
I’m sure I’m overlooking something simple but I can’t find it. Can someone show me how to do this?

Answer 1

John Saunders is right: this isn’t really possible. The “right” way to do what you’re trying to do is to create a class that represents the key-value pairs you’re really trying to return, and then return an IEnumerable of that class. For example:

public class AppSetting
{
    public string Name {get;set;}
    public string Value {get;set;}
}

    [WebMethod]
    public IEnumerable<AppSetting> ReadAppSettings()
    {
        return AppSettings.Settings.Select(
            kvp => new AppSetting{Name = kvp.Key, Value = kvp.Value});
    }

This provides the data straight to the consumer: let them decide whether they want to represent this as a Dictionary/Hashtable, List, Array, Tree, or any other data structure they decide to make of it. All you care about from a data-integrity standpoint is making sure each key is tied to the right value.