How to pass parameters or query strings to the top navigation in _Layout.cshtml in ASP.NET

Question

In my controller I have three parameters. (GET:/Class/List)

public class ClassController : Controller {
    public ActionResult List(string classCode = null, string className = null, List<string> semester = null)
    { ... }
}

And I got this in my navbar...

<a class="nav-link text-dark" asp-area="" asp-controller="Class" asp-action ="List">Classes</a>

I want to pass a value of parameter semester so that the link looks like localhost/Class/List?semester=9&semester=1. Thanks!

I tried ViewBag and asp-route-id, but failed.

Answer 1

This may not work because your ActionResult List expects a list of strings. In my experience, a list of strings usually requires you to loop through Model -> item.semester to list all the values ​​in the view.

You can try changing List<string> to a single string.

public ActionResult List(string classCode = null, string className = null, string semester = null)

Then append this to the "a" tag. Let's say you populate a Viewbag.semesterId in your controller.

asp-semester="@ViewBag.semesterId"

Answer 2

You can try to convert List to query string. operate:

public IActionResult A()
{
    ViewBag.List = new List<string> { "a", "b", "c" };
  
    return View();

}

A.cshtml：

@{
    var list=ViewBag.List as List<string>;
    var result = "?semester=" +String.Join("&semester=", list);
}
<a class="nav-link text-dark" href="/Class/List@(result)">Classes</a>

result: