Question about using Reflection

[Tjossul]

Hello,

using Reflection seems to be quite different in the nanoFramework.

Lets say I have a class Configuration with properties that are classes with properties:

`

public class Configuration
{
    public string HtmlTitle { get; set; } = "Configuration";

    public Setting1 Setting1 { get; set; } = new Setting1();
    public Setting2 Setting2 { get; set; } = new Setting2();
    public Setting3 Setting3 { get; set; } = new Setting3();
}

public class Setting1
{
    public string Setting1Parameter1 { get; set; } = "Setting1Parameter1Value";
    public string Setting1Parameter2 { get; set; } = "Setting1Parameter2Value";
    public string Setting1Parameter3 { get; set; } = "Setting1Parameter3Value";
}

public class Setting2
{
    public string Setting2Parameter1 { get; set; } = "Setting2Parameter1Value";
    public string Setting2Parameter2 { get; set; } = "Setting2Parameter2Value";
    public string Setting2Parameter3 { get; set; } = "Setting2Parameter3Value";
}

public class Setting3
{
    public string Setting3Parameter1 { get; set; } = "Setting3Parameter1Value";
    public string Setting3Parameter2 { get; set; } = "Setting3Parameter2Value";
    public string Setting3Parameter3 { get; set; } = "Setting3Parameter3Value";
}

`

I could get all settings with its values with something like this:

`

    static void Main(string[] args)
    {
        var configuration = new Configuration();

        var propertiesOuter = configuration.GetType().GetProperties();

        foreach (var propertyOuter in propertiesOuter)
        {
            var valueOuter = propertyOuter.GetValue(configuration);
            Console.WriteLine($"{propertyOuter.Name}: {valueOuter}");

            if (valueOuter == null || valueOuter?.GetType()?.FullName?.StartsWith("System") == true)
            {
                Console.WriteLine(Environment.NewLine);

                continue;
            }

            var propertiesInner = valueOuter?.GetType().GetProperties();

            if (propertiesInner == null)
                continue;

            foreach (var propertyInner in propertiesInner)
            {
                var valueInner = propertyInner.GetValue(valueOuter);
                Console.WriteLine($"{propertyInner.Name}: {valueInner}");
            }

            Console.WriteLine(Environment.NewLine);
        }

        Console.ReadLine();
    }

Result:

HtmlTitle: Configuration

Setting1: TestLoopFieldInfo.Setting1
Setting1Parameter1: Setting1Parameter1Value
Setting1Parameter2: Setting1Parameter2Value
Setting1Parameter3: Setting1Parameter3Value

Setting2: TestLoopFieldInfo.Setting2
Setting2Parameter1: Setting2Parameter1Value
Setting2Parameter2: Setting2Parameter2Value
Setting2Parameter3: Setting2Parameter3Value

Setting3: TestLoopFieldInfo.Setting3
Setting3Parameter1: Setting3Parameter1Value
Setting3Parameter2: Setting3Parameter2Value
Setting3Parameter3: Setting3Parameter3Value

`

But how can I do this in the nanoFramework? I do not have the possibility to call the properties like this

`

var propertiesOuter = configuration.GetType().GetProperties();

`

The "Reflection" samples sadly does not contain the information I am looking for - I think.

Thank you in advance for your answers!

Regards.
T.

[josesimoes]

.NET nanoFramework reflection API is as close as possible to the full framework.
Recall that this is called nano for a reason! 😉 There are compromisses that where required to have Reflection implemented.
You have to work with the API that's available...

[Ellerbach]

And all the available methods are here: https://docs.nanoframework.net/api/System.Type.html#methods

You can already do a lot of thigs. As an example, there is quite a complex logic on the Json serializer here: https://github.com/nanoframework/nanoFramework.Json/blob/38bdfd113c257300409997782db8f230390b9898/nanoFramework.Json/JsonSerializer.cs#L73

[Tjossul]

Hey guys,

I have the feeling that you both feel attacked in any way because of my words?! "josesimoes" you did not really answer but wrote more something like a justification. But you really do not need to, I like your work very much. English is not my mother language so please forgive me using not the right words.

My problem may be that Reflection is not my hobbyhorse. I found a solution in my desktop app (published above), but I seem to be at the beginning again here and sadly with nearly no progress.

I started with

var configuration = new Configuration();
var methods = configuration.GetType().GetMethods();

foreach (var method in methods)
{
   if (!Helper.IsRelevantMethod(method)) // this is a similar Method to "ShouldSerializeMethod" that you are using in your JsonSerializer
        continue;

   Debug.WriteLine(method.Name); // Gives me the property names -> "get_" + name

   var returnType = method.ReturnType;

   Debug.WriteLine(returnType.Name); // Gives me the property return types (String, Setting1, Setting2, Setting3)
}

But I do not know how to get the properties of the Setting1, Setting2, Setting3 and how to get the values. When I started this discussion I hoped that you could show me the right direction, that you could help me with that a little bit.

Thanks again.
T.

[Tjossul]

Hi networkfusion and josesimoes,

thank you for your answers. I implemented your "JsonConfigurationStore" in my app using my "Configuration" class above, yes. This works great. The reason I want to use Reflection is to reduce maintanance in new projects... I have a configuration class which is different in every project. But I want automatically displayed all settings with its values on my configuration website. These are allways SSID and password and then project related settings. I would like to add a configuration class to the new project and the part of displaying and changing the values on the configuration website should work without changing the code. What do you think about that? Not a good idea?

networkfusion, I did not read the Json sample completely until now (it is really huge) but I will. In your OrgPalThreeDemo you know the property names - I think I understood this part (MqttConfigFileSchema config = (MqttConfigFileSchema)JsonConvert.DeserializeObject(File.ReadAllText(file), typeof(MqttConfigFileSchema)); and following lines). But I do not know the properties, only the structure of the configuration class keeps the same. So, your example is great and I will have a look deeper later because of the subject MQTT but it sadly didn't help at this point.

Thank you very much for your suggestions.

T.

[networkfusion]

Maybe try to think of the problem in reverse, with the nF board having a set of known values and the website [service] performing the reflection. It is definitely worth looking into how this is performed for settings "shadows/twins" as used for our MQTT libs for "AWS/Azure".

[Tjossul]

OK, thank you, I will have a look into it.

[Ellerbach]

I have something that generates automatically web pages for configurations. The code is here: https://github.com/Ellerbach/LegoTrain/blob/main/SharedServices/Controllers/ConfigurationController.cs

It's fully using reflection, you just need to have the configuration class being based on a common interface which can be totally empty if you want. As you'll see in the code, it will find all the methods, the associated types and generate the proper control. Special case for bools as in javascript in the forms, you have to keep the state. It does also with convention supports things like password depending on your naming conventions.

[Tjossul]

Hey Ellerbach,

this is exactly what I was looking for thank you. And the values I get through the Invoke method... I thought of that. But the right way I missed.

Thank you very much!

Cheers.
T.