从自定义模型装订器调用默认模型装订器？

Question

我编写了一个自定义模型绑定器,它应该根据当前文化来映射来自URL-Strings(GET)的日期(这里的旁注:如果你使用GET作为http-call,默认模型绑定器不考虑当前的文化...).

public class DateTimeModelBinder : IModelBinder
{

    #region IModelBinder Members
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {

        if (controllerContext.HttpContext.Request.HttpMethod == "GET")
        {
            string theDate = controllerContext.HttpContext.Request.Form[bindingContext.ModelName];
            DateTime dt = new DateTime();
            bool success = DateTime.TryParse(theDate, System.Globalization.CultureInfo.CurrentUICulture, System.Globalization.DateTimeStyles.None, out dt);
            if (success)
            {
                return dt;
            }
            else
            {
                return null;
            }
        }

        return null; // Oooops...

    }
    #endregion
}

我在global.asax中注册了模型绑定器:

ModelBinders.Binders.Add(typeof(DateTime?), new DateTimeModelBinder());

现在问题发生在最后return null;.如果我使用POST的其他表单,它将用null覆盖已映射的值.我怎么能避免这个？

任何输入的Thx.sl3dg3

Answer 1

派生自然DefaultModelBinder后调用基本方法:

public class DateTimeModelBinder : DefaultModelBinder
{
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        // ... Your code here

        return base.BindModel(controllerContext, bindingContext);
    }

}

Answer 2

好吧，这实际上是一个微不足道的解决方案：我创建一个默认绑定器的新实例并将任务传递给他：

public class DateTimeModelBinder : IModelBinder
{

#region IModelBinder Members
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{

    if (controllerContext.HttpContext.Request.HttpMethod == "GET")
    {
        string theDate = controllerContext.HttpContext.Request.Form[bindingContext.ModelName];
        DateTime dt = new DateTime();
        bool success = DateTime.TryParse(theDate, System.Globalization.CultureInfo.CurrentUICulture, System.Globalization.DateTimeStyles.None, out dt);
        if (success)
        {
            return dt;
        }
        else
        {
            return null;
        }
    }

    DefaultModelBinder binder = new DefaultModelBinder();
    return binder.BindModel(controllerContext, bindingContext);

}
#endregion
}