public override IModelBinder GetBinder(ModelBindingExecutionContext modelBindingExecutionContext, ModelBindingContext bindingContext)
        {
            ModelBinderUtil.ValidateBindingContext(bindingContext);

            string keyFieldName   = ModelBinderUtil.CreatePropertyModelName(bindingContext.ModelName, "key");
            string valueFieldName = ModelBinderUtil.CreatePropertyModelName(bindingContext.ModelName, "value");

            if (bindingContext.UnvalidatedValueProvider.ContainsPrefix(keyFieldName) && bindingContext.UnvalidatedValueProvider.ContainsPrefix(valueFieldName))
            {
                return(ModelBinderUtil.GetPossibleBinderInstance(bindingContext.ModelType, typeof(KeyValuePair <,>) /* supported model type */, typeof(KeyValuePairModelBinder <,>) /* binder type */));
            }
            else
            {
                // 'key' or 'value' missing
                return(null);
            }
        }