What is Validation in ASP.NET Core? See Example

Validation in ASP.NET Core ensures that user input meets specific rules before processing. It improves data integrity, security, and user experience. ASP.NET Core supports data annotations, custom validation, and client-side validation integrated with Razor views.

Key Features:

• Use data annotations like [Required], [EmailAddress], [Range]
• Supports client-side and server-side validation
• Works with MVC, Razor Pages, and Web API
• Custom validators for complex scenarios
• Improves security and user experience

Example:
Model with validation attributes:

public class UserModel
{
    [Required]
    public string Username { get; set; }

    [Required]
    [EmailAddress]
    public string Email { get; set; }

    [Required]
    [StringLength(20, MinimumLength = 6)]
    public string Password { get; set; }
}

Razor view with validation summary:

<form asp-action="Register" method="post">
    <input asp-for="Username" />
    <input asp-for="Email" />
    <input asp-for="Password" type="password" />
    <button type="submit">Register</button>
    <span asp-validation-summary="All"></span>
</form>

Validation in ASP.NET Core ensures reliable data and provides feedback to users, reducing errors and enhancing app stability.

Citations:

• Learn more on Savanka
• Official ASP.NET Core Documentation