When would you use a constructor, a static factory method, or a builder to create an object in C#?

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I use a constructor for one clear creation path, a named factory for multiple or fallible paths, and a builder for genuinely complex staged assembly. An Order constructor can require customer identity and keep the new order valid. Order.TryCreate can return validation errors without throwing for expected input failure, while Order.Restore can make a separate persistence path explicit. A builder is useful for complex configuration, but it is excessive for three required values. Object initializers suit simple data shapes, not invariant bypasses.

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Valid construction, required state, named creation paths, result types, optional parameters, builders, dependency injection, and object initializers.

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I use a constructor when required inputs are small and construction has one clear meaning. A static factory helps when creation needs a name, validation result, subtype choice, caching, or more than one meaningful path. A builder helps assemble many optional parts or a staged complex object.
I use a constructor for one clear creation path, a named factory for multiple or fallible paths, and a builder for genuinely complex staged assembly. An Order constructor can require customer identity and keep the new order valid. Order.TryCreate can return validation errors without throwing for expected input failure, while Order.Restore can make a separate persistence path explicit. A builder is useful for complex configuration, but it is excessive for three required values. Object initializers suit simple data shapes, not invariant bypasses.
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Factories can hide concrete implementation selection and centralize defaults, but they should not become service locators. Dependencies needed for ongoing behavior are usually injected into the service that coordinates creation rather than stored on a domain object. Builders should validate at Build and avoid producing partially valid objects earlier. Required members improve compiler guidance for data models, though runtime validation still protects external input.

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Using a builder for every small object.
Performing network I/O in a constructor.
Using object initializers to bypass required invariants.
Turning a factory into a general service locator.

When would you use a constructor, a static factory method, or a builder to create an object in C#?

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