Question

I have a website that is using the following code to return a repository, it will accept an interface and return the firt implementation it finds, however, I think the code is too slow and causing issues, is there any better ways to implement this?

Thanks

 public T For<T>() where T : class
    {
        T returnVar = null;
        Assembly asm = Assembly.GetExecutingAssembly();

        var types = asm.GetTypes().Where(x => x.IsClass == true && x.Namespace != null && x.Namespace.StartsWith("Website.Core.Data.Repositories"));

        var result = types.Where(x => x.GetInterface(typeof(T).Name) != null);

        foreach (var x in result)
        {    
            var mi = x.GetConstructors();
            returnVar = (T)asm.CreateInstance(x.UnderlyingSystemType.ToString());
        }

        if (returnVar != null)
            return returnVar;
        else
            throw new Exception("No Repository for: " + typeof(T).Name);        
    }

Answer 1

How about this:

private readonly Dictionary<Type, object> _items = new Dictionary<Type, object>();

    public T For<T>() where T : class
    {
        Type serviceType = typeof (T);
        lock (_items)
        {
            object instance;
            if (_items.TryGetValue(serviceType, out instance))
                return (T) instance;
        }


        Assembly asm = Assembly.GetExecutingAssembly();
        var types = asm.GetTypes().Where(x => x.IsClass
                                              && !x.IsAbstract
                                              && serviceType.IsAssignableFrom(x)
            );

        T returnVar = null;
        foreach (Type x in types)
        {
            ConstructorInfo[] mi = x.GetConstructors();
            returnVar = (T) asm.CreateInstance(x.UnderlyingSystemType.ToString());
        }

        if (returnVar != null)
        {
            lock (_items)
                _items.Add(serviceType, returnVar);
            return returnVar;
        }
        throw new Exception("No Repository for: " + typeof (T).Name);
    }