I’m working on an ASP.NET Core application and I have a base controller that defines a method to set a header title using ViewBag. I want to utilize this method in my Razor views to display dynamic header titles.
Here is the base controller with the SetHeaderTitle method:
public abstract class BaseController
{
protected void SetHeaderTitle(string headerName)
{
ViewBag.HeaderTitle = headerName;
}
}
In my derived controller, I call this method inside the constructor:
public class MaterialConstantNumbersController : BaseController
{
private const string HeaderName = "Constant numbers section";
public MaterialConstantNumbersController(IMediator mediator) : base(mediator)
{
SetHeaderTitle(headerName: HeaderName);
}
}
However, when the Razor page loads, the header title does not display.
What could be causing the ViewBag.HeaderTitle to not display in the Razor view?
What is the best approach to set and display different header titles for each controller in my application?
I am using dependency injection for IMediator in my controllers.
The Razor view where I am trying to display the header title is set up to access ViewBag.HeaderTitle.
I have placed to call this method in all actions but this approach is not solid at all and it is repetitive work.
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1
The main reason of this approach does not work correctly as you expected is that the constructor runs before the action method and viewBag
sets during the action method execution.
there are 2 steps you can take into account:
1- Move setHeaderTitle to an action filter:
instead of setting the header title in the constructor you can create an action filter to set it
before the action method execution. This ensures that the viewbag is properly set up before the view is rendered.
public class HeaderTitleFilter : ActionFilterAttribute
{
private readonly string _headerTitle;
public HeaderTitleFilter(string headerTitle)
{
_headerTitle = headerTitle;
}
public override void OnActionExecuting(ActionExecutingContext context)
{
var controller = context.Controller as Controller;
if (controller != null)
{
controller.ViewBag.HeaderTitle = _headerTitle;
}
base.OnActionExecuting(context);
}
}
and in controller
[HeaderTitleFilter(HeaderName)]
public class MaterialConstantNumbersController{}
2- Override onactionexecuting in your baseController to set the header title before any action method execution.
public abstract class BaseController : Controller
{
protected virtual string HeaderTitle { get; set; }
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
base.OnActionExecuting(filterContext);
ViewBag.HeaderTitle = HeaderTitle;
}
}
public class MaterialConstantNumbersController : BaseController
{
private const string HeaderName = "Constant numbers section";
public MaterialConstantNumbersController(IMediator mediator) : base()
{
HeaderTitle = HeaderName;
}
}
Hope these help you.
1
1.It is not possible to call the SetHeaderTitle method in the Controller Constructor, it needs to be called in every Action.
2.You are using dependency injection for IMediator in your controllers.I think you have some mistakes.so I wrote an example for you.
Here’s an example：
1). BaseController.cs
using MediatR;
using Microsoft.AspNetCore.Mvc;
namespace webApi2.Controllers
{
public abstract class BaseController : Controller
{
private readonly IMediator _mediator;
public BaseController(IMediator mediator) {
_mediator = mediator;
}
protected void SetHeaderTitle(string headerName)
{
ViewBag.HeaderTitle = headerName;
}
}
}
2). ProductsController.cs
using MediatR;
using Microsoft.AspNetCore.Mvc;
namespace webApi2.Controllers
{
public class ProductsController : BaseController
{
private readonly IMediator _mediator;
private const string HeaderName = "Constant numbers section";
public ProductsController(IMediator mediator) : base(mediator)
{
_mediator = mediator;
}
public IActionResult Index()
{
SetHeaderTitle(headerName: HeaderName);
return View();
}
}
}
3). index.cshtml
The result is as follows: