Data Validation and Integrity in .NET Applications

Introduction

Ensuring data validation and integrity is critical in .NET applications to maintain accurate, consistent, and reliable data throughout the application lifecycle. Proper validation prevents bad data from entering the system, while integrity mechanisms ensure data remains consistent and trustworthy.

1. What Is Data Validation?

Data validation checks whether the input data is correct, complete, and meets the application’s requirements before processing or storing it.

Examples:

Required fields are filled

Email addresses are properly formatted

Numbers fall within allowed ranges

Dates are valid

2. What Is Data Integrity?

Data integrity ensures that the data stored in a system is accurate, consistent, and protected against corruption, unauthorized modification, or loss.

Types of data integrity:

Entity Integrity: Primary keys are unique and not null.

Referential Integrity: Foreign keys correctly link related data.

Domain Integrity: Data adheres to defined data types and constraints.

User-Defined Integrity: Business rules and logic.

3. Data Validation Techniques in .NET

a. Data Annotations

Using attributes in models to enforce validation rules.

Example:

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using System.ComponentModel.DataAnnotations;

public class User

{

    [Required(ErrorMessage = "Username is required")]

    [StringLength(50, MinimumLength = 3)]

    public string Username { get; set; }

    [Required]

    [EmailAddress(ErrorMessage = "Invalid email address")]

    public string Email { get; set; }

    [Range(18, 100, ErrorMessage = "Age must be between 18 and 100")]

    public int Age { get; set; }

}

b. Fluent Validation

A popular library to create flexible and reusable validation rules outside models.

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public class UserValidator : AbstractValidator<User>

{

    public UserValidator()

    {

        RuleFor(user => user.Username).NotEmpty().Length(3, 50);

        RuleFor(user => user.Email).EmailAddress();

        RuleFor(user => user.Age).InclusiveBetween(18, 100);

    }

}

c. Model Binding & Validation in ASP.NET Core

When using MVC or API controllers, the framework automatically validates models decorated with data annotations:

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[HttpPost]

public IActionResult CreateUser([FromBody] User user)

{

    if (!ModelState.IsValid)

    {

        return BadRequest(ModelState);

    }

    // Proceed with valid user

}

4. Maintaining Data Integrity

a. Database Constraints

Primary Keys: Ensure uniqueness and identify each record.

Foreign Keys: Enforce valid relationships between tables.

Unique Constraints: Prevent duplicate data.

Check Constraints: Enforce domain rules (e.g., Age > 0).

b. Transactions

Use database transactions to ensure a group of operations either all succeed or fail together, maintaining data consistency.

Example in Entity Framework Core:

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using var transaction = await dbContext.Database.BeginTransactionAsync();

try

{

    // Multiple data changes

    await dbContext.SaveChangesAsync();

    await transaction.CommitAsync();

}

catch

{

    await transaction.RollbackAsync();

    throw;

}

c. Concurrency Control

Handle simultaneous data updates to prevent conflicts using:

Optimistic Concurrency: Check a timestamp or version number before saving.

Pessimistic Concurrency: Lock records during editing.

EF Core example with a concurrency token:

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[Timestamp]

public byte[] RowVersion { get; set; }

5. Best Practices

Always validate both client-side and server-side to prevent bad data and improve user experience.

Use ViewModels or DTOs for validation, not directly your database models.

Leverage built-in ASP.NET Core validation features.

Enforce database-level constraints as a last line of defense.

Use logging and monitoring to detect integrity violations.

Implement unit and integration tests to verify validation and integrity rules.

Summary

Concept Description Example in .NET

Data Validation Ensures data meets rules before processing Data Annotations, FluentValidation

Data Integrity Ensures data remains consistent and correct DB Constraints, Transactions, Concurrency Control

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