Tutorials ASP.NET Core MVC Mastery
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Mastering Action Results in ASP.NET Core
Every request must end with an IActionResult. Professional developers understand that choosing the correct return type is vital for performance and API usability.
The IActionResult Hierarchy
IActionResult is an interface. For more advanced scenarios in Web API, we use ActionResult<T>, which allows for better documentation (Swagger) and return values.
Section 1: The UI Group (Views & More)
- ViewResult: Standard HTML View rendering.
- PartialViewResult: Render a small HTML fragment for AJAX calls.
- JsonResult: Standard for JSON responses. Internal serializer handles the mapping.
Section 2: The "Navigation" Group (Redirects)
1. RedirectToActionResult
RedirectToAction("Index", "Home"); - Perfect for keeping users moving after a POST action.
2. LocalRedirectResult
For security, only redirects within the same app. This prevents Open Redirect Attacks.
Section 3: The "Binary" Group (Files & Data)
When you need to download a PDF or stream an image, use FileResult.
public IActionResult DownloadInvoice(int id) {
var pdfBytes = ExportToPDF(id);
return File(pdfBytes, "application/pdf", "Invoice.pdf");
}
Architect Insight: Custom Action Results
For complex enterprise apps, creating a Custom ActionResult (e.g. CsvResult) to handle specific formatting globally can save hundreds of lines of code. This ensures consistent data formatters across the entire application.
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