Use PuppeteerSharp to load the page, wait until the span exists, select it with a CSS selector, read its innerText property, and convert the result to a C# string. The essential extraction is GetPropertyAsync("innerText") followed by JsonValueAsync<string>(). If QuerySelectorAsync finds no match, it returns null, so production code should check the handle before reading it.
Minimal working example
This console-style example launches a headless browser, opens a page, finds span.price, and prints the rendered text. Replace the URL and selector with those used by your page.
using PuppeteerSharp;
await new BrowserFetcher().DownloadAsync();
await using var browser = await Puppeteer.LaunchAsync(new LaunchOptions { Headless = true });
await using var page = await browser.NewPageAsync();
await page.GoToAsync("https://example.com");
var span = await page.QuerySelectorAsync("span.price");
if (span is null)
{
throw new InvalidOperationException("The span selector did not match an element.");
}
var textHandle = await span.GetPropertyAsync("innerText");
var text = await textHandle.JsonValueAsync<string>();
Console.WriteLine(text);QuerySelectorAsync performs a selector lookup in the current page and returns an element handle for the first match. The handle represents an in-page DOM element. When there is no match, the result is null; it is not an empty element that can safely be dereferenced.
Prepare a selector that identifies the right span
The selector is the part most likely to break when a site’s markup changes. Prefer a stable class, an attribute intended for testing, or a meaningful component hook. For example, span.price is clearer than a positional expression such as “the third span.” If several spans share a class, decide whether you need the first match or every match before choosing between the single-element and collection APIs.
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- Single known value: use
QuerySelectorAsync("span.price"). - Repeated values: use
QuerySelectorAllAsync("span.result"). - Markup added by JavaScript: wait for the selector before querying it.
- Custom traversal or fallback behavior: evaluate a function in the page context.
Scrape a span that is rendered after navigation
Navigation can finish before client-side code inserts the target span. Call WaitForSelectorAsync after navigation and before the query. The PuppeteerSharp API describes this operation as waiting for a selector to be added to the DOM.
await page.GoToAsync("https://example.com/product");
await page.WaitForSelectorAsync("span.price");
var span = await page.QuerySelectorAsync("span.price");
if (span is null)
{
throw new InvalidOperationException("The price span was not rendered.");
}
var text = await (await span.GetPropertyAsync("innerText"))
.JsonValueAsync<string>();
Console.WriteLine(text);Keep the selector used for waiting identical to the selector used for extraction. If the wait completes but the subsequent query is still null, check whether the page changed its markup, navigated again, or placed the content inside a frame.
Extract text from several spans
QuerySelectorAllAsync returns the collection form of selector lookup. Iterate over the handles and apply the same property-extraction pattern to each one. The order is the order returned by the page’s selector query.
var spans = await page.QuerySelectorAllAsync("span.result");
var values = new List<string>();
foreach (var item in spans)
{
var value = await (await item.GetPropertyAsync("innerText"))
.JsonValueAsync<string>();
values.Add(value);
}
foreach (var value in values)
{
Console.WriteLine(value);
}An empty collection is different from a null single-element handle: it means the collection query matched no elements. Treat that as an expected condition when a result list can legitimately be empty, or raise an error when at least one value is required.
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Use page-side evaluation for custom extraction
When you need a fallback, nested lookup, or a small piece of JavaScript logic, evaluate a function in the page context. This example returns an empty string when the selector does not match.
var text = await page.EvaluateFunctionAsync<string>(
"selector => document.querySelector(selector)?.innerText ?? ''",
"span.price");
Console.WriteLine(text);EvaluateFunctionAsync is available on the Page and Frame APIs. Use it when the extraction rule is easier to express in JavaScript than as a sequence of element-handle operations. For strict data pipelines, the explicit null check shown earlier is usually preferable because it reports a missing selector instead of silently producing an empty value.
Choose the right extraction pattern
| Situation | API pattern | Result to handle |
|---|---|---|
| One span in already-loaded markup | QuerySelectorAsync then GetPropertyAsync("innerText") |
A single element handle, or null when there is no match |
| Span inserted after navigation | WaitForSelectorAsync, then the single-element pattern |
The wait must target the same selector you intend to read |
| Several matching spans | QuerySelectorAllAsync and a loop |
A collection that can contain zero or more handles |
| Custom JavaScript or nullable fallback | EvaluateFunctionAsync<string> |
The function’s returned string, including an intentionally chosen empty fallback |
Handle missing spans deliberately
A null handle normally means one of three things: the selector is wrong, the content has not been inserted yet, or the query is running in the wrong document context. Include both the URL and selector in your exception so a failed job can be diagnosed without reproducing it interactively.
var url = "https://example.com/product";
var selector = "span.price";
await page.GoToAsync(url);
await page.WaitForSelectorAsync(selector);
var span = await page.QuerySelectorAsync(selector);
if (span is null)
{
throw new InvalidOperationException(
$"No element matched '{selector}' at {url}.");
}
var value = await (await span.GetPropertyAsync("innerText"))
.JsonValueAsync<string>();If an absent span is valid for a particular page, use the evaluation fallback or return a nullable result from your own method instead of throwing. The important choice is to make the missing-data policy explicit.
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When the span is inside an iframe
Selector queries run against the current page or frame. If the visible span belongs to an iframe, obtain that frame first and perform the same WaitForSelectorAsync, QuerySelectorAsync, and property-extraction operations against the frame’s page context. Querying the top-level page will not find an element that exists only inside the embedded document.
After switching frames, keep the selector specific to that frame and include the frame URL or identifying attribute in diagnostic messages. This prevents a valid selector from being mistaken for a missing element simply because it was evaluated in the wrong context.
Reliability and performance practices
- Reuse a page when appropriate. If a job visits many URLs, avoid launching a new browser for every span. Navigate the existing page, extract the value, and then continue.
- Wait narrowly. Wait for the target selector rather than relying only on navigation completion; this reduces races with client-side rendering.
- Batch repeated values. Use
QuerySelectorAllAsynconce and iterate over the returned handles instead of issuing a separate selector query for each position. - Keep selectors stable. Prefer semantic classes or data attributes over positional selectors that change when unrelated markup is inserted.
- Dispose resources. Use
await usingfor browser and page resources in long-running jobs so processes do not accumulate open browser instances. - Do not claim a benchmark that does not exist. The official API material for these operations provides behavior and signatures, not a published extraction-speed figure. Measure your own workload if throughput matters.
Troubleshooting common failures
QuerySelectorAsync returns null
Verify the selector in the page’s final DOM, then add WaitForSelectorAsync if JavaScript inserts the span after navigation. Also verify that you are querying the correct frame.
The wait never reaches the extraction code
The selector may never be added, may differ between states, or may be rendered only after an action. Confirm the exact selector and the page state required to produce it. If the element is optional, use a nullable or page-side fallback rather than waiting for a required element.
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The returned string is empty
Check that the matched node is the intended span and that the page has reached the state containing its text. For custom rules, inspect the function passed to EvaluateFunctionAsync and decide whether an empty fallback is masking a selector mismatch.
The script works once but fails in a long-running process
Ensure browser and page objects are disposed with await using. Keep failure messages tied to the URL and selector so intermittent navigation or markup changes can be identified from logs.
The selector finds a different value after a redesign
Replace positional selectors with a stable class or data attribute, and add a test that asserts the extracted value is present before saving it.
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The service has 63 capture options, including full-page screenshots with lazy images loaded, CSS-selector element capture, dark mode, device and viewport settings, retina scale, PDF paper and margin controls, custom CSS and JavaScript, click-before-capture actions, selector or network-idle waits, request and resource blocking, custom headers, cookies, user agents, authorization, timezone and geolocation, transparent backgrounds, resizing, configurable caching, signed image links, asynchronous webhooks, bulk capture of up to 100 URLs per call, a usage API, and an OpenAPI specification. Parameter names used by other screenshot APIs are accepted to ease migration.
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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com/product -o shot.webpimport requests
r = requests.get(
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params={"access_key": "YOUR_API_KEY", "url": "https://example.com/product"},
timeout=90,
)
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});
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