Question

I’ve been tinkering with a CMS that I’m making as a personal project and I have got to a point that I am stuck on.

Basically I have a plugin manager that loads assemblies at runtime, looks for methods marked with a custom attribute and makes these methods available to be called from a template engine I have wrote.

I have the template engine parsing the template into expressions which get compiled into a function that I can cache and call. There are little bits of code within this template that are parsed to do different things like call a method on a plugin.

Example of the template code:

So far I have this parsed correctly, I have the method name and parameters as strings, ints, bools etc..

The plugin manager I have wrote is working fine too but I’m having trouble wiring the two together.

Say for example this is a plugin class:

[Plugin(Name="Test")]
public class TestPlugin
{
    private DateTime _startTime;

    public TestPlugin()
    {
        _startTime = DateTime.Now;
    }

    [TemplateAction]
    public string Test(int number, string testString)
    {
        return "TEST";
    }
}

I need to be able to call Test() from my parsed template and pass in any parameters from the template to the method. I have created a System.Delegate from the method marked with the attribute and added an expression within the template engine as part of the cached method to call the Test().

What I don’t know is how to pass in the parsed parameters from the template into the method. I tried to create an object[] and pass that into DynamicInvoke on the delegate but it complained about argument mismatch so I’m a bit stuck. I’m not sure if you can pass object[] into a method that has (params object[] args) as a signature via expressions.

Performance is also a concern with DynamicInvoke so if there is a way to accomplish this without using DynamicInvoke or create something I can cache that would be great.

Sorry if its unclear, any questions feel free to ask.

Any help is much appreciated.

Rick.

UPDATE

Okay after some thinking and thanks to D Stanley I did this.

foreach (var method in type.GetMethods().Where(x => x.GetCustomAttributes(typeof(TemplateActionAttribute), true).Length > 0))
{
    if (method.ReturnType != typeof(string)) continue;

    PluginTemplateActions.Add(method.Name, o => (string)method.Invoke(plugin, o));
}

So far it works just the way I want but will this also be quicker than DynamicInvoke?

Answer 1

You could use reflection:

TestPlugin plugIn = new TestPlugin();
object[] params = null //... set parameters here
MethodInfo mi = typeof(TestPlugin).GetMethod("Test");
mi.invoke(plugIn,params);