Tutorials for maintainers of real applications
Web Forms still runs the back office. Here is how to keep it working.
Postback Notes publishes short, complete examples for ASP.NET Web Forms, C#, ADO.NET and SQL Server, plus the jQuery and CSS that sit on top of them. Every page is written for .NET Framework 4.8 unless it says otherwise, uses parameterised SQL, encodes its output and links to the Microsoft, MDN or jQuery reference it relies on.
Most consulted
- Get and set a TextBox value with JavaScriptClientID, ClientIDMode and what the server sees after a postback
- 100 interview questions on ASP.NET, C#, SQL Server and OOPShort, accurate answers grouped by topic
- SQL injection and how to prevent itParameters, safe dynamic SQL, allow-lists and least privilege
- Enable or disable a TextBox with jQueryprop(), preventDefault and why disabled fields are not posted
- Set a DropDownList selection from scriptBy value or text, with AutoPostBack and event validation
- Fade in and out with a CSS3 transitionOpacity, visibility and reduced motion
- Parser Error after deploymentCould not load type, application folders, CLR versions
- Unable to serialize the session stateStateServer, SQL Server session and [Serializable]
Sections
- ASP.NETWeb Forms controls, postbacks, configuration, deployment errors and the server-side patterns that still run a great many intranet and line-of-business sites.
- C# & ADO.NETC# language questions and data access with ADO.NET and SQL Server: commands, readers, DataSets, parameters, files and e-mail.
- OOP & conceptsObject-oriented programming in C#, framework comparisons, interview preparation and the security basics every .NET developer is asked about.
- jQuery & JavaScriptReading and changing Web Forms controls from the browser: client IDs, validation, events, effects and small DOM utilities.
- HTML & CSSCSS3 transitions, tooltips and HTML elements explained with standalone examples you can paste into a file and open.
Latest tutorials
- Get and set an ASP.NET TextBox value with JavaScript
How to read and change the text of an ASP.NET Web Forms TextBox from plain JavaScript: finding the rendered id with ClientID and ClientIDMode, the value property, multiline boxes, read-only and disabled boxes, and what the server sees after a postback.
- Get and set an ASP.NET TextBox value with jQuery
Using jQuery's val() to read and write an ASP.NET Web Forms TextBox: selectors that survive ClientID rewriting, reacting to input, setting values in GridView rows, and keeping the posted value on the server.
- Enable or disable an ASP.NET TextBox on a button click with jQuery
Toggle an ASP.NET TextBox between enabled and disabled from a button click using jQuery's prop(), without an unwanted postback, and understand what disabled, readonly and the server-side Enabled property each do to the posted value.
- Set an ASP.NET DropDownList's selected value or text with JavaScript and jQuery
Select an item of an ASP.NET DropDownList from the browser by value or by visible text, with plain JavaScript and with jQuery, fire AutoPostBack when needed, and avoid event validation and 'multiple items selected' errors on the server.
- SQL injection: what it is and how to prevent it in ASP.NET and SQL Server
How SQL injection works, a vulnerable ADO.NET login query and how it is exploited, and the defences that actually work in C# and SQL Server: parameterised commands, safe stored procedures and sp_executesql, allow-lists for identifiers and least privilege.
- 100 interview questions on ASP.NET, C#, SQL Server and OOP, with short answers
One hundred questions that come up in .NET developer interviews, grouped by topic, each with a short, accurate answer: OOP, C# language, ASP.NET Web Forms and MVC, ADO.NET, SQL Server, web basics and security.
- Choosing hosting for an ASP.NET website: what to check before you pay
A vendor-neutral guide to hosting ASP.NET applications: Web Forms on Windows and IIS versus ASP.NET Core on Linux or Windows, shared hosting, VPS and cloud platforms, SQL Server options, the technical checklist, and how to test a host before migrating.
- Fade in and fade out with a CSS3 transition
Build fade-in and fade-out effects with the CSS transition property: opacity with visibility so hidden elements stop catching clicks, hover and class-toggle versions, timing functions, fading on page load with keyframes, and respecting prefers-reduced-motion.
- CSS3 tooltip: show and hide hint text with a transition
An accessible tooltip built with HTML and CSS3 transitions: positioning with absolute and transform, an arrow drawn with a pseudo-element, showing on hover and keyboard focus, aria-describedby, the Escape key, and using it next to ASP.NET form fields.
- Parser Error when deploying an ASP.NET application: causes and fixes
How to read the ASP.NET 'Parser Error' and 'Configuration Error' pages after a deployment, and fix the usual causes: Could not load type, wrong CodeBehind vs CodeFile, missing bin assemblies, application not configured in IIS, allowDefinition=MachineToApplication, duplicate config sections and framework version mismatches.