--- title: ASP.NET 2.0 Event Validation | daily.dev description: Event Validation in ASP.NET 2.0 checks that postbacks genuinely originate from the controls that triggered them, guarding against malicious tampering, and is... canonical: https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: ASP.NET 2.0 Event Validation | daily.dev og:description: Event Validation in ASP.NET 2.0 checks that postbacks genuinely originate from the controls that triggered them, guarding against malicious tampering, and is... og:url: https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos og:image: https://api.daily.dev/og/posts/wdROKSuos.png og:image:alt: ASP.NET 2.0 Event Validation 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. # ASP.NET 2.0 Event Validation **[Maarten Balliauw](https://daily.dev/sources/maartenballiauw)** · 2 min read · 0 upvotes · 0 comments ## Summary Event Validation in ASP.NET 2.0 checks that postbacks genuinely originate from the controls that triggered them, guarding against malicious tampering, and is enabled by default. A user control nested on a master page triggered an 'Invalid postback or callback argument' error because its inner controls weren't recognized as valid sources. Rather than disabling event validation via the Page directive or Web.config, the recommended fix is overriding the control's Render method to explicitly register each inner control's UniqueID with RegisterForEventValidation before rendering. ## 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 fix 'Invalid postback or callback argument' error from a user control on a master page in ASP.NET 2.0? Override the Render method of the user control and register each inner control's UniqueID with Page.ClientScript.RegisterForEventValidation before calling base.Render. This tells ASP.NET's event validation that postbacks from those controls are legitimate, avoiding the need to disable EnableEventValidation globally in Web.config or per-page, which weakens security. _Developers debugging ASP.NET Web Forms postback errors can find similar fixes curated on daily.dev._ ### What does Event Validation do in ASP.NET 2.0? Event Validation adds a security check on postback actions, verifying that a postback claimed to come from a specific control on the client side genuinely originated from that control rather than from a malicious actor attempting to forge requests. It is enabled by default, providing protection even when developers forget to add their own security checks. _Teams hardening ASP.NET Web Forms apps can track security-relevant framework behavior on 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 - [Protect Your Entities with Domain Validation](https://daily.dev/posts/protect-your-entities-with-domain-validation-rha9t8ic8) · Telerik · 3 upvotes · 0 comments - [The silent filter: How an ASP.NET MVC quirk became a security leak](https://daily.dev/posts/the-silent-filter-how-an-asp-net-mvc-quirk-became-a-security-leak-wec0w8625) · The Art of Simplicity · 2 upvotes · 0 comments - [Blocked Up](https://daily.dev/posts/blocked-up-fpacgahcr) · The Daily WTF · 0 upvotes · 0 comments --- Tags: [#aspnet](https://daily.dev/tags/aspnet), [#c#](https://daily.dev/tags/c#), [#web-security](https://daily.dev/tags/web-security) [View this post on daily.dev](https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos) ```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":"ASP.NET 2.0 Event Validation","url":"https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos"},"datePublished":"2026-10-04T13:06:17.852Z","dateModified":"2026-10-15T02:22:42.926Z","description":"Event Validation in ASP.NET 2.0 checks that postbacks genuinely originate from the controls that triggered them, guarding against malicious tampering, and is...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/af0ef0faf84112f27f97ccdc2c970860?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/af0ef0faf84112f27f97ccdc2c970860?_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/asp-net-2-0-event-validation-wdroksuos","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"aspnet,c#,web-security","timeRequired":"PT2M"} {"@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":"ASP.NET 2.0 Event Validation"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/asp-net-2-0-event-validation-wdroksuos#faq","mainEntity":[{"@type":"Question","name":"How do I fix 'Invalid postback or callback argument' error from a user control on a master page in ASP.NET 2.0?","acceptedAnswer":{"@type":"Answer","text":"Override the Render method of the user control and register each inner control's UniqueID with Page.ClientScript.RegisterForEventValidation before calling base.Render. 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