ASP.NET FromBody

last modified April 3, 2025

In this article, we explore the FromBody attribute in ASP.NET 8. This attribute is crucial for binding HTTP request body data to action method parameters.

ASP.NET is a cross-platform framework for building modern web applications. FromBody enables complex data binding from JSON or XML request bodies.

Basic Definition

The FromBody attribute in ASP.NET indicates that a parameter should be bound using the request body. It's primarily used with POST, PUT, and PATCH requests.

When applied to a parameter, FromBody tells the model binder to use the content-type header to select an appropriate formatter. JSON is the most common format for request bodies.

FromBody is essential for Web APIs that accept complex data structures. It works with the built-in JSON serializer to deserialize request bodies.

ASP.NET FromBody Example

The following example demonstrates a Web API controller using FromBody to create and update products.

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();

var app = builder.Build();

app.MapControllers();
app.Run();

This sets up a basic ASP.NET application with controller support. The AddControllers method configures services needed for controllers.

using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private static List<Product> _products = new()
    {
        new Product(1, "Laptop", 999.99m),
        new Product(2, "Mouse", 19.99m),
        new Product(3, "Keyboard", 49.99m)
    };

    [HttpPost]
    public IActionResult CreateProduct([FromBody] Product product)
    {
        if (product == null) return BadRequest();
        
        product.Id = _products.Max(p => p.Id) + 1;
        _products.Add(product);
        
        return CreatedAtAction(nameof(GetProductById), 
            new { id = product.Id }, product);
    }

    [HttpPut("{id}")]
    public IActionResult UpdateProduct(int id, [FromBody] Product product)
    {
        if (product == null || product.Id != id) 
            return BadRequest();
            
        var existingProduct = _products.FirstOrDefault(p => p.Id == id);
        if (existingProduct == null) return NotFound();
            
        existingProduct.Name = product.Name;
        existingProduct.Price = product.Price;
            
        return NoContent();
    }

    [HttpGet("{id}")]
    public IActionResult GetProductById(int id)
    {
        var product = _products.FirstOrDefault(p => p.Id == id);
        if (product == null) return NotFound();
        return Ok(product);
    }
}

public record Product(int Id, string Name, decimal Price);

This controller demonstrates two different scenarios using FromBody. The first method creates a new product from the request body sent as JSON.

The second method updates an existing product by ID, with the updated data coming from the request body. Both methods validate the input data.

The CreatedAtAction result in the create method returns a 201 status code with the Location header pointing to the new resource. The update method returns 204 No Content on success.

The example shows how FromBody automatically deserializes JSON request bodies into Product objects. The ApiController attribute enables automatic model validation and error responses.

Source

Microsoft ASP.NET Web API Documentation

In this article, we have explored the FromBody attribute in ASP.NET 8. This powerful feature simplifies binding complex data from HTTP request bodies.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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