📄 playwright-python/dotnet/docs/api/class-worker

File: class-worker.md | Updated: 11/18/2025

Source: https://playwright.dev/dotnet/docs/api/class-worker

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The Worker class represents a WebWorker . worker event is emitted on the page object to signal a worker creation. close event is emitted on the worker object when the worker is gone.

page.Worker += (_, worker) =>{    Console.WriteLine($"Worker created: {worker.Url}");    worker.Close += (_, _) => Console.WriteLine($"Worker closed {worker.Url}");};Console.WriteLine("Current Workers:");foreach(var pageWorker in page.Workers){    Console.WriteLine($"\tWorker: {pageWorker.Url}");}

Methods​

EvaluateAsync​

Added before v1.9 worker.EvaluateAsync

Returns the return value of expression .

If the function passed to the Worker.EvaluateAsync() returns a Promise , then Worker.EvaluateAsync() would wait for the promise to resolve and return its value.

If the function passed to the Worker.EvaluateAsync() returns a non-Serializable value, then Worker.EvaluateAsync() returns undefined. Playwright also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity.

Usage

await Worker.EvaluateAsync(expression, arg);

Arguments

  • expression string #

    JavaScript expression to be evaluated in the browser context. If the expression evaluates to a function, the function is automatically invoked.

  • arg EvaluationArgument ? (optional)#

    Optional argument to pass to expression .

Returns

  • [object]#

EvaluateHandleAsync​

Added before v1.9 worker.EvaluateHandleAsync

Returns the return value of expression as a JSHandle .

The only difference between Worker.EvaluateAsync() and Worker.EvaluateHandleAsync() is that Worker.EvaluateHandleAsync() returns JSHandle .

If the function passed to the Worker.EvaluateHandleAsync() returns a Promise , then Worker.EvaluateHandleAsync() would wait for the promise to resolve and return its value.

Usage

await Worker.EvaluateHandleAsync(expression, arg);

Arguments

  • expression string #

    JavaScript expression to be evaluated in the browser context. If the expression evaluates to a function, the function is automatically invoked.

  • arg EvaluationArgument ? (optional)#

    Optional argument to pass to expression .

Returns

Url​

Added before v1.9 worker.Url

Usage

Worker.Url

Returns

Events​

event Close​

Added before v1.9 worker.event Close

Emitted when this dedicated WebWorker is terminated.

Usage

Worker.Close += async (_, worker) => {};

Event data