带有数据对象的ASP.NET Core重定向

Question

I'm making a Action method in a controller like following.

In Model

public class Model
{
    public string modelStr { get; set; }
}

In Controller

public IActionResult ActionMethod1(Model value) 
{
    return View(value); ---- debug point (1)
}

public IActionResult ActionMethod2(int pageKind)
{
    Model temp = new Model();

    if (pageKind == 1)
    {
        temp.modelStr = "Hi ASP.NET Core";
    }
    else
    {
        temp.modelStr = "error!";
    }

    return RedirectToAction("ActionMethod1", temp); ---- debug point (2)
}

And I access ActionMethod2 with /Controller/ActionMethod2 in browser. I expected /Controller/ActionMethod1 will be called and its model value has value which is sent by ActionMethod2 .

But if I debug it, 1) debuger do not stop at debug point (2) and at debug point (1) the value has no value, ie value.modelStr == null .

How do value at debug point (1) get a value from ActionMethod2 ?

Answer 1

This is caused by parameter binding .

The parameter value of ActionMethod1 is type of Model class, this is a complex type, mvc will try to bind it's value from http body, the http request should be a POST request.

But ActionMethod2 returns a RedirectToAction result, the browser redirect to ActionMethod1 with GET , and can not handle by ActionMethod1 .

The answer is add FromQueryAttribute to the parameter value of ActionMethod1 , tells mvc that value is bind from query string, like this:

public IActionResult ActionMethod1([FromQuery]Model value) 
{
    return View(value); ---- debug point (1)
}

Now ActionMethod1 will handle GET request, and ActionMethod2 can redirect to it.

Answer 2

What you're trying to do is not possible. However there are work-arounds. One common approach is to add the data to the TempData dictionary and retrieve it in the other method:

public IActionResult ActionMethod1()
{
    var value = (Model)TempData["model"];

    return View(value);
}

public IActionResult ActionMethod2(int pageKind)
{
    Model temp = new Model();

    if (pageKind == 1)
    {
        temp.modelStr = "Hi ASP.NET Core";
    }
    else
    {
        temp.modelStr = "error!";
    }

    TempData["model"] = temp;

    return RedirectToAction("ActionMethod1");
}

Alternatively, are you sure you even need to actually redirect the user? You could always just call the method directly:

public IActionResult ActionMethod1(Model value)
{
    return View(value);
}

public IActionResult ActionMethod2(int pageKind)
{
    Model temp = new Model();

    if (pageKind == 1)
    {
        temp.modelStr = "Hi ASP.NET Core";
    }
    else
    {
        temp.modelStr = "error!";
    }

    return ActionMethod1(temp);
}