How to Get/Set Properties using the C# client API in XSockets

Question

In the XSockets Server API there is an example on how to get/set properties on the server controller using the JavaScript API

Get/Set properties from the client APITop

If you have a property with a public getter or setter you can access the getter/setter methods from the client API’s

public string MyProp {get;set;}

The property above can be retrieved and changed from the client API’s (both JavaScript and C#). Example on how to set a new value from JavaScript

conn.publish('set_MyProp',{value:'NewValue'});

See the client API’s for more information.

But there's no information whatsoever on the Client API's page

I'm having a hard-time figuring out what is the equivalent C# Client code for the JavaScript code conn.publish('set_MyProp',{value:'NewValue'});

Any help is immensely appreciated.

Answer 1

Well, I've found out the hard way, by trial an error, that this:

Client.Send(new { value = "NewValue" }, "set_MyProp");

Is the equivalent code to:

conn.publish('set_MyProp',{value:'NewValue'});

Pay attention to the case of "value"!!! Don't capitalize the word!

UPDATE

I've created two extension methods which makes it very easy to get and set property values (there's also a WaitForConnection which is useful in somewhat synchronous scenarios like Unit Testing).

Since XSockets is (very unfortunately) not open source, and documentation is minimal, I have to guess how things work, so my extension methods may not be as efficient and elegant as they could be if I was able to read the source code, and I may have been a little too "careful" with my approach for reading properties from the server... If anyone knows how to improve it, please, edit the answer or suggest it on the comments section:

public static class XSocketClientExtensions
{
    public static bool WaitForConnection(this XSocketClient client, int timeout=-1) {
        return SpinWait.SpinUntil(() => client.IsConnected, timeout);
    }

    public static void SetServerProperty(this XSocketClient client, string propertyName, object value) {
        client.Send(new { value = value }, "set_" + propertyName);
    }

    public static string GetServerProperty(this XSocketClient client, string propertyName) {
        var bindingName = "get_" + propertyName;
        // why event name is lowercase? 
        var eventName = bindingName.ToLowerInvariant();
        // we must be careful to preserve any existing binding on the server property
        var currentBinding = client.GetBindings().FirstOrDefault(b => b.Event == eventName);
        try {
            // only one binding at a time per event in the client
            if (currentBinding != null)
                client.UnBind(bindingName);
            var waitEvent = new ManualResetEventSlim();
            string value = null;
            try {
                client.Bind(bindingName, (e) => {
                    value = e.data;
                    waitEvent.Set();
                });
                // we must "Trigger" the reading of the property thru its "event" (get_XXX)
                client.Trigger(bindingName);
                // and wait for it to arrive in the callback
                if (waitEvent.Wait(5000))
                    return value;
                throw new Exception("Timeout getting property from XSockets controller at " + client.Url);
            } finally {
                client.UnBind(bindingName);
            }
        } finally {
            // if there was a binding already on the "property getter", we must add it back
            if (currentBinding != null) 
                client.Bind(bindingName, currentBinding.Callback);
        }
    }
}

Usage is a breeze:

// Custom controller
public class MyController : XSocketController
{
    public int Age { get; set; }

    public override void OnMessage(ITextArgs textArgs) {
        this.SendToAll(textArgs);
    }
}

// then in the client
var client = new XSocketClientEx("ws://127.0.0.1:4502/MyController", "*");
client.WaitForConnection(); // waits efficiently for client.IsConnected == true
client.SetServerProperty("Age", 15);
int age = Convert.ToInt32(client.GetServerProperty("Age"));

You can skip the following, it is just a rant!

A few things made it difficult to nail it down from the beginning. There's no agreement between the JavaScript client and the C# client. So what you learn in one does not translate to the other technology. On my own multi-language client APIs I try to make all APIs behave and look very similar, if not identical, so code is almost portable. I've got an API that looks nearly identical in both JavaScript, C# and Java.

The differences that bothered me are:

1. The methods have different names: publish in JavaScript vs Send in C#
2. The parameters are passed in reversed order: value, event in C#, event, value in JavaScript
3. Not a difference in itself, but if you use 'Value' in the C# example it won't work, you must use 'value'... I don't believe it should have been case sensitive... the reasoning for this is quite convincing. I'll quit quibbling then!

Answer 2

I agree, the API's between JavaScript and C# should have been more similar. As of 4.0 they will both support both pub/sub and rpc and have the same naming on the interfaces.

The setting/getting of properties will have methods that help you since there is a difference in setting Enums and Strings for example. So the API will have methods like.. (note that you will multiplex over n controllers on 1 connections, that why the controller name is specified)

C#

conn.Controller("NameOfController").SetEnum("name", "value");
conn.Controller("NameOfController").SetProperty("name", object);

JavaScript

conn.nameofcontroller.setEnum('name', 'value');
conn.nameofcontroller.setProperty('name', object);

---

Regarding the error if you capitalize the "value" parameter in C#... Since we use the methods that the compiler created for public getters and setters value is really a parameter on a method and should not ever be capitalized.