ASP.NET MVC5 creating custom validation attribute is not working

Question

I have the following validation attribute:

public class AtLeastOneAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        bool retval = false;
        if (((IEnumerable<object>)value).Count() > 0)
        {
            retval = true;
        }
        return retval;
    }
}

My custom model binder:

public class CartOrderBinder : IModelBinder
{
private const string sessionKey = "CartOrder";

public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
    CartOrder model = null;
    if (controllerContext.HttpContext.Session[sessionKey] != null)
    {
        model = (CartOrder)controllerContext.HttpContext.Session[sessionKey];
    }
    if (model == null)
    {
        model = new CartOrder();
        if (controllerContext.HttpContext.Session != null)
        {
            controllerContext.HttpContext.Session[sessionKey] = model;
        }
    }
    return model;
}

}

This is how I applied the attribute on my model's property:

[AtLeastOne]
public List<CartProduct> Products = new List<CartProduct>();

The problem is that this validation is not working. If I don't have a product in my cart list it still returns true.

Why is this happening?

Answer 1

I found the problem. The MVC doesn't want to see public List<CartProduct> Products = new List<CartProduct>(); as a property. So I had to change this into public List<CartProduct> Products {get;set;} and create an instance of for my products repository in my model binder.

But still, is there any way I can avoid this problem and still use the public List<CartProduct> Products = new List<CartProduct>(); ? It would be very useful to create the instance in my model.