Custom

Custom Drawing and Owner-Draw

How MFC lets you take over rendering of standard controls — buttons, list boxes, combo boxes, list controls — through the owner-draw mechanism and custom-draw…

Custom Markup Extensions

How to author a custom MarkupExtension by overriding ProvideValue, and when to reach for one instead of a converter or plain binding.

Custom Controls and User Controls

Compare WPF's two approaches to building reusable controls — lightweight, composition-based UserControl versus fully templatable, lookless custom Control.

Aggregate and Custom Accumulators

Learn how LINQ's Aggregate() operator implements a general-purpose fold, letting you build custom accumulation logic beyond Sum, Count, and Average.

Custom LINQ Extension Methods

Learn how to write your own LINQ-style extension methods on IEnumerable<T>, including deferred execution with yield return and chaining conventions.

Custom Connectors

Build custom connectors to let Power Apps and Power Automate call your own REST APIs with proper authentication and actions.

Writing Custom Matchers

Learn how to extend Jest's expect with expect.extend() to write custom matchers that produce clearer, more expressive assertions and failure messages.

API Keys and Custom Headers

Learn how to authenticate requests using API keys and how to work with custom HTTP headers in Postman, including placement options and common conventions.

Custom Commands

Learn how to extend Cypress with Cypress.Commands.add() to create reusable custom commands like cy.login(), reducing duplication across tests.

Custom Data Tests

When the four built-in generic tests aren't enough, dbt lets you write singular tests as standalone SQL files or custom generic tests as reusable, parameterize…

Custom Visuals

How to source, vet, and build custom Power BI visuals beyond the built-in gallery, from AppSource certification to the pbiviz SDK.

Custom Forms

SharePoint list and library forms can be customized with Power Apps or JSON column formatting to improve data entry accuracy and the end-user experience.

HTTP and Custom Connectors

Call external REST APIs from Power Automate using the HTTP action and build reusable custom connectors with authentication and defined schemas.

Custom Events and Payloads

Learn how to design well-structured custom event names and payload shapes in Socket.IO, including validation, versioning, and binary data handling for maintain…

Socket.IO with React

Integrate Socket.IO cleanly into React using a context provider, custom hooks, and correct connection lifecycle management.

Custom Types and Structs

Learn how to define composite types with struct, control mutability and construction, use parametric fields for performance, and attach behavior via multiple d…

Custom Resource Definitions

How CustomResourceDefinitions let you extend the Kubernetes API with your own resource types, including schema validation, versioning, and subresources.

Custom Scalars

How to model domain-specific leaf values beyond GraphQL's five built-in scalars using serialize, parseValue, and parseLiteral.

Directives in GraphQL

Understand built-in and custom GraphQL directives, how they alter query execution and schema behavior, and where to apply them safely.

Custom Exceptions in Java

Learn how to define and throw your own checked or unchecked exception classes in Java for clearer, domain-specific error handling.

Custom Exceptions in Python

How to define your own exception classes to represent domain-specific errors, and how to raise and chain them properly.

Custom Errors in JavaScript

Building your own Error subclasses by extending the built-in Error class to represent domain-specific failures.

Custom Errors and errors.Is/As in Go

Build custom error types in Go and use errors.Is and errors.As to inspect and match wrapped errors.

CSS Custom Properties (Variables)

Learn how to define and reuse values across a stylesheet using CSS custom properties and the var() function.

Go Error Handling Cheat Sheet

Covers Go's explicit error return values, wrapping errors with %w, errors.Is and errors.As, custom error types, and panic/recover semantics.