如何在MVC动作C＃中获得可选参数

Question

There is an TestAction in HomeController as below:

    public ActionResult TestAction(string a = "a", int b = 2, int c = 1)
    {
        var DATA = Request.Params;//Can't get param neither a nor b
        return View();
    }

If my visit link is "/Home/TestAction?c=23". Then DATA will be {c=23}, but not contain a and b. Does there any way to get these two params to make DATA like {a="a", b=2, c=23} by visit link "/Home/TestAction?c=23". (These params are different in different page, so can't hard-code).

Answer 1

You can do it by passing the params in the url as following. The model binder will read the query string and pass these parameter values to the action method.

/Home/TestAction?a=valuea&b=valueb

You can also use the route data to pass the value. An appropriate route will need to be defined to do that.

Answer 2

Take all the paramters as nullable int?, string accepts null by default. So after changes your method will look like

public ActionResult TestAction(string a, int? b, int? c)
{
   //Check conditions for null here
    return View();
}