Models and ViewModels in ASP.NET Core

Introduction

The Job Portal needs JobSeeker, JobListing, and Company entities — but you should not expose domain models directly to Razor. ViewModels shape data for each screen and carry validation rules.

After this article you will

• Distinguish domain models, view models, and DTOs
• Apply Data Annotations for validation
• Build Job Portal view models from scratch
• Validate models in controllers with ModelState

Prerequisites

• Article 8 — Layouts, Partial Views and View Components
• ShopNest.Web project from prior lessons

Concept deep-dive

public class JobApplyViewModel
{
    [Required][StringLength(100)]
    public string FullName { get; set; }

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

    [Range(0, 50)]
    public int YearsExperience { get; set; }

    [Required]
    public IFormFile Resume { get; set; }
}

In controller: if (!ModelState.IsValid) return View(model);. AutoMapper (Article 50) maps entity ↔ view model at scale.

Hands-on — ShopNest Job Portal

1. Define entities: JobSeeker, Company, JobListing.
2. Create JobSearchViewModel with filters (location, keyword, min salary).
3. JobDetailsViewModel combines listing + company + apply form.
4. Validate POST apply action; show field errors in view.

Common errors & best practices

• Over-posting: bind only safe properties — use view models, not entities, on forms.
• Missing [Required] on nullable value types — use Required or nullable reference types.

Interview questions

Q: Why not pass JobListing entity to view?
A: Over-posting, circular references, leaking internal fields; view models expose only what UI needs.

Q: Data Annotations vs FluentValidation?
A: Annotations on model; FluentValidation separate classes — better for complex rules (Article 39).

Summary

• Domain models map to DB; view models map to screens
• Data Annotations drive server validation
• Job Portal demonstrates search and apply view models

Previous: Layouts, Partial Views and View Components
Next: Forms, Model Binding and Validation

FAQ