Asp.Net Core Returning Json Views And Status Codes Complete Guide

Top 10 Questions and Answers: ASP.NET Core Returning JSON, Views, and Status Codes

1. How do you return a JSON result from a controller action in ASP.NET Core?

public IActionResult GetUsers()
{
    var users = new List<User>
    {
        new User { Id = 1, Name = "John Doe" },
        new User { Id = 2, Name = "Jane Doe" }
    };
    return Json(users);
}

Alternatively, you can use the Ok method with JsonConvert.SerializeObject() if required:

public IActionResult GetUsers()
{
    var users = new List<User>
    {
        new User { Id = 1, Name = "John Doe" },
        new User { Id = 2, Name = "Jane Doe" }
    };
    return Ok(new JsonResult(users));
}

The Json method automatically serializes the object to JSON format.

2. How do you return a view in ASP.NET Core?

Returning a view in ASP.NET Core is done using the View method, which renders a view and returns it as an HTML response. Here's an example:

public IActionResult UserProfile()
{
    var user = new User { Id = 1, Name = "John Doe" };
    return View(user); // Pass user data to the view
}

In this example, the framework will look for a view named UserProfile.cshtml in the Views/ folder by default and send it as a response.

3. How can you return a partial view in ASP.NET Core?

To return a partial view, use the PartialView method. This is useful when you want to load only a part of a view, often used with AJAX requests.

public IActionResult UserProfilePartial()
{
    var user = new User { Id = 1, Name = "John Doe" };
    return PartialView("UserProfilePartial", user);
}

The PartialView method looks for a view named UserProfilePartial.cshtml.

4. How do you return a custom status code in ASP.NET Core?

You can return custom status codes using the StatusCode method. For example, returning a 404 Not Found:

public IActionResult GetUser(int id)
{
    var user = GetUserById(id);
    if (user == null)
    {
        return StatusCode(404, "User not found");
    }
    return Ok(user);
}

You can also use more specific methods like NotFound, BadRequest, or Ok to return appropriate status codes.

5. How can you return a custom JSON response with a status code in ASP.NET Core?

To return a JSON response along with a custom status code, combine Json with StatusCode:

public IActionResult GetUser(int id)
{
    var user = GetUserById(id);
    if (user == null)
    {
        return StatusCode(404, new { message = "User not found" });
    }
    return StatusCode(200, user); // or return Ok(user);
}

Alternatively, using specific methods:

public IActionResult GetUser(int id)
{
    var user = GetUserById(id);
    if (user == null)
    {
        return NotFound(new { message = "User not found" });
    }
    return Ok(user);
}

6. Can you return multiple types of result from a single controller action in ASP.NET Core?

Yes, you can return multiple types of results from a single controller action based on certain conditions. For example:

public IActionResult GetUser(int id, bool? partial)
{
    var user = GetUserById(id);
    if (user == null)
    {
        return NotFound();
    }
    if (partial == true)
    {
        return PartialView("UserProfilePartial", user);
    }
    return View(user);
}

7. How do you control the JSON serialization process in ASP.NET Core?

You can customize JSON serialization by configuring Microsoft.AspNetCore.Mvc.JsonOptions. This is often done in the Startup.cs file:

services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.PropertyNamingPolicy = null; // Disable camelCase
        options.JsonSerializerOptions.WriteIndented = true; // Pretty print
    });

Alternatively, you can use the [JsonSerializerOptions] attribute on the method to apply settings locally.

8. How do you configure a custom response format for all actions in ASP.NET Core?

To configure a custom response format globally, use the AddControllersWithViews or AddControllersAsServices methods and configure the serialization options:

services.AddControllersWithViews()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.PropertyNamingPolicy = null; // Disable camelCase
        options.JsonSerializerOptions.WriteIndented = false; // Compact JSON
    });

9. How can you return a file from a controller action in ASP.NET Core?

To return a file, use the File method. This can be useful for serving images, documents, or other files directly from a controller.

public IActionResult GetResume()
{
    var path = Path.Combine(_env.WebRootPath, "resumes", "john_doe_resume.pdf");
    var fileContent = System.IO.File.ReadAllBytes(path);
    return File(fileContent, "application/pdf", "john_doe_resume.pdf");
}

10. How do you return a No Content (204) response in ASP.NET Core?

To return a 204 No Content response, use the NoContent method:

public IActionResult DeleteUser(int id)
{
    var user = GetUserById(id);
    if (user == null)
    {
        return NotFound();
    }
    // Delete user logic here
    return NoContent();
}

The NoContent method sends a 204 response with no body content, indicating successful request processing with no return.