--- title: Form validation with ASP.NET MVC preview 5 | daily.dev description: ASP.NET MVC preview 5 introduces built-in form validation support via the ViewData.ModelState collection, replacing manual validation implementations from... canonical: https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Form validation with ASP.NET MVC preview 5 | daily.dev og:description: ASP.NET MVC preview 5 introduces built-in form validation support via the ViewData.ModelState collection, replacing manual validation implementations from... og:url: https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh og:image: https://api.daily.dev/og/posts/N2EjB15uH.png og:image:alt: Form validation with ASP.NET MVC preview 5 og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Form validation with ASP.NET MVC preview 5 **[Maarten Balliauw](https://daily.dev/sources/maartenballiauw)** · 3 min read · 0 upvotes · 0 comments ## Summary ASP.NET MVC preview 5 introduces built-in form validation support via the ViewData.ModelState collection, replacing manual validation implementations from earlier previews. A controller example shows how to add model errors using ModelState.AddModelError and check validity with ModelState.IsValid. The view uses two new HtmlHelper extension methods, ValidationMessage and ValidationSummary, to display field-level and summary validation errors. An update notes that the controller's UpdateModel method can also populate ModelState errors automatically when the model throws an exception. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I validate form input in ASP.NET MVC preview 5? ASP.NET MVC preview 5 lets you add validation errors directly to the ViewData.ModelState collection using AddModelError, then check ViewData.ModelState.IsValid before processing the form. In the view, two new HtmlHelper methods, ValidationMessage and ValidationSummary, render field-level and overall error messages, replacing manual validation logic required in earlier previews. _daily.dev surfaces practical framework walkthroughs like this for developers wiring up form validation._ ### What is the difference between ModelState.AddModelError and UpdateModel for handling validation in ASP.NET MVC? AddModelError manually adds a named error with a message to ViewData.ModelState, used when writing custom checks like empty fields or invalid email format. UpdateModel instead updates a model object directly from posted form values, and automatically adds any exceptions thrown during that update into the same ViewData.ModelState dictionary. _developers comparing model-binding approaches can track framework patterns like these via daily.dev._ ## Similar posts on daily.dev - [Advanced Form Validation in Blazor 10](https://daily.dev/posts/advanced-form-validation-in-blazor-10-zzayx40g4) · Telerik · 1 upvotes · 0 comments - [Customizing Validation Messages in Blazor Forms](https://daily.dev/posts/customizing-validation-messages-in-blazor-forms-iozh3bh3e) · Telerik · 1 upvotes · 0 comments - [Protect Your Entities with Domain Validation](https://daily.dev/posts/protect-your-entities-with-domain-validation-rha9t8ic8) · Telerik · 3 upvotes · 0 comments --- Tags: [#webdev](https://daily.dev/tags/webdev), [#c#](https://daily.dev/tags/c#) [View this post on daily.dev](https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Form validation with ASP.NET MVC preview 5","url":"https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh"},"datePublished":"2026-10-04T13:06:10.330Z","dateModified":"2026-10-04T13:14:14.484Z","description":"ASP.NET MVC preview 5 introduces built-in form validation support via the ViewData.ModelState collection, replacing manual validation implementations from...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/25689ef71a86ba307e5febd202dfde9c?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/25689ef71a86ba307e5febd202dfde9c?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Maarten Balliauw","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Maarten Balliauw","logo":"https://media.daily.dev/image/upload/s--rOTg3VYO--/f_auto,q_auto/v1791119043/logos/maartenballiauw?_a=BAMAMicg0","url":"https://daily.dev/sources/maartenballiauw"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"webdev,c#","timeRequired":"PT3M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Maarten Balliauw","item":"https://daily.dev/sources/maartenballiauw"},{"@type":"ListItem","position":3,"name":"Form validation with ASP.NET MVC preview 5"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/form-validation-with-asp-net-mvc-preview-5-n2ejb15uh#faq","mainEntity":[{"@type":"Question","name":"How do I validate form input in ASP.NET MVC preview 5?","acceptedAnswer":{"@type":"Answer","text":"ASP.NET MVC preview 5 lets you add validation errors directly to the ViewData.ModelState collection using AddModelError, then check ViewData.ModelState.IsValid before processing the form. 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