C# Interview Question #169

What is model validation in ASP.NET Core?

ASP.NET Core, DI & Middleware Senior Advanced

Quick Interview Answer

Model validation verifies that incoming data satisfies declared validation rules.

Detailed Explanation

Model validation verifies that incoming data satisfies declared validation rules.

Data annotation attributes such as Required, StringLength, Range, and EmailAddress can define common rules. More complex business validation can be handled in application services or dedicated validation libraries.

With controllers marked ApiController, invalid model state can automatically produce an HTTP 400 response using the framework's API behavior.

Code Example

public class CreateProductRequest
{
    [Required]
    [StringLength(200)]
    public string Name { get; set; } = string.Empty;

    [Range(0.01, 1000000)]
    public decimal Price { get; set; }
}