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Customized typemapper #1

@smolesen

Description

@smolesen

Hi

It would be nice if it was possible to customize the mapping. For example be able to map based on a convention saying that the eventhandler must start with subject from event.
If you refactor the EventGridOptions to take a mapper, then one can extend the maping with own requirements
//Default mapper
`public class EventGridMapper
{
private readonly Dictionary<string, Type> handlers = new Dictionary<string, Type>();

    public virtual void AddMapping(string eventType, Type type)
    {
        handlers.Add(eventType.ToLower(), type);
    }

    public virtual Type LookUp(Event item)
    {
        var resulttype = handlers.FirstOrDefault(i => i.Key == item.EventType.ToLower());
        return resulttype.Equals(default(KeyValuePair<string, Type>)) ? null : resulttype.Value;
    }
}

`

//Mapper that will map to handlers starting with subject, fx. {Subject}_SomeEventHandler public class SubjectEventGridMapper : EventGridMapper
{
private readonly Dictionary<string, List> handlers = new Dictionary<string, List>();

    public override void AddMapping(string eventType, Type type)
    {
        if (handlers.Any(h => h.Key == eventType.ToLower()))
            handlers[eventType].Add(type);
        else
           handlers.Add(eventType.ToLower(), new List<Type> { type });

    }

    public override Type LookUp(Event item)
    {
        var key = item.EventType.ToLower();
        if (handlers.ContainsKey(key) && handlers[key].Any(t => t.Name.StartsWith(item.Subject + "_")))
            return handlers[key].First(t => t.Name.StartsWith(item.Subject + "_"));
        return null;
    }

}

``using System;
using SharpEventGrid;
namespace SharpEventGridServer
{
public class EventGridOptions
{
protected Type _defaultMapping;

    internal IServiceProvider ServiceProvider { get; set; }

    public string EventsPath { get; set; } = "api/events";
    public bool AutoValidateSubscription { get; set; } = true;
    public Action ValidateSubscriptionCallBack { get; set; }
    public string ValidationKey { get; set; }
    public string ValidationValue { get; set; }
    public Action<string, bool, string> AutoValidateSubscriptionAttemptNotifier { get; set; }
    public EventGridMapper Mapper = new EventGridMapper();
    public virtual void MapEvent<T>(string eventType) where T : IEventGridHandler
    {
        Mapper.AddMapping(eventType, typeof(T));
    }
    public void MapDefault<T>() where T : IEventGridHandler
    {
        _defaultMapping = typeof(T);
    }

    public void SetValidationKey(string key, string value)
    {
        ValidationKey = key;
        ValidationValue = value;
    }

    internal virtual IEventGridHandler ResolveHandler(Event item)
    {
        var typeToCreate = Mapper.LookUp(item);
        if (typeToCreate == null)
            typeToCreate = _defaultMapping;
        var handler = ServiceProvider.GetService(typeToCreate) ?? Activator.CreateInstance(typeToCreate);
        return (IEventGridHandler)handler;
    }
}

}``

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