To make stepping through the modelbinding process easier

Asp.Net MVC DebuggableModelBinder and CheckboxToBoolModelBinder.md

Use the DebuggableModelBinder with a breakpoint to investigate what's happening when your complex model isn't binding as you expect.

Use the CheckBoxToBoolModelBinder to bind <input type="checkbox" > Note the Html standard describes "on" as the only valid postable value for a checkbox.. If you're posting something else, change the code. And don't that forget that unchecked means that nothing gets posted.

In either case, wire them up with e.g.:

public class MvcApplication : HttpApplication
{
    protected void Application_Start()
    {
        //
        // ...
        //
        ModelBinders.Binders.Add(typeof(bool), new CheckboxToBoolBinder());
        ModelBinders.Binders.Add(typeof(MyComplexTypeThatsHavingProblems), new DebuggableModelBinder());
    }

CheckBoxToBoolModelBinder.cs

    public class CheckboxToBoolBinder : DefaultModelBinder
    {
        public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
            if (value != null)
            {
                if (value.AttemptedValue == "on" || value.AttemptedValue == "true" )
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            else
            {
                return base.BindModel(controllerContext, bindingContext);
            }
        }
    }

Debuggable ModelBinder.cs

    public class DebuggableModelBinder : DefaultModelBinder
    {
        protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor)
        {
            if (propertyDescriptor.Name == "WhateverPropertyNameImHavingDifficultyWith")
            {
                var attemptedValue=bindingContext.ValueProvider.GetValue(propertyDescriptor.Name).AttemptedValue;
                Console.WriteLine("Raw value : " + attemptedValue);
            }

            base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
        }

        public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var result= base.BindModel(controllerContext, bindingContext);
            return result;
        }

        protected override bool OnPropertyValidating(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, object value)
        {
            var result = base.OnPropertyValidating(controllerContext, bindingContext, propertyDescriptor, value);
            if (!result)
            {
                Console.WriteLine("Here");
            }
            return result;
        }

        public static void Config(params Type[] types)
        {
            foreach (var type in types)
            {
                ModelBinders.Binders.Add(type, new DebuggableModelBinder());
            }
        }
    }