unoplatform/uno · error · Error

BrowserHtmlElement: Element with id '${id}' not found.

Error message

BrowserHtmlElement: Element with id '${id}' not found.

What it means

Thrown by the private getElementOrThrow helper in BrowserNativeElementHostingExtension when document.getElementById(id) returns null. This means the C# side (a BrowserHtmlElement / native element host) requested an HTML element by ID that does not exist in the current DOM.

Source

Thrown at src/Uno.UI.Runtime.Skia.WebAssembly.Browser/ts/Runtime/BrowserNativeElementHostingExtension.ts:231

			return String(eval(command) || "");
		}

		public static async invokeAsync(command: string): Promise<string> {
			// Preseve the original emscripten marshalling semantics
			// to always return a valid string.
			var result = await eval(command);

			return String(result || "");

		}

		/**
		 * Returns the element with the given id, or throws an error if not found.
		 */
		private static getElementOrThrow(id: string): HTMLElement {
			const element = document.getElementById(id);
			if (!element) {
				throw new Error(`BrowserHtmlElement: Element with id '${id}' not found.`);
			}
			return element as HTMLElement;
		}
	}
}

View on GitHub (pinned to 0418340488)

Solutions

1. Verify the element id string passed from C# matches the id attribute set on the DOM element at insertion time.
2. Ensure the HTML element is attached to the DOM before issuing the getElement call (wait for the element's Loaded event).
3. Check that the element was not disposed/removed by a visual-tree update between insertion and retrieval.

Example fix

// before: id does not exist in DOM yet
const el = document.getElementById('my-div-42'); // null → throws

// after: ensure the element is created and appended before retrieval
const el = document.createElement('div');
el.id = 'my-div-42';
document.body.appendChild(el);
// now getElementOrThrow('my-div-42') succeeds

// Verify element exists before requesting it via the interop
if (!document.getElementById(id)) {
    console.warn(`Element ${id} not in DOM yet`);
    return null;
}

try {
    // call the native element hosting interop
} catch (e) {
    if (e.message.includes("not found")) {
        // element was removed or never inserted — retry after DOM update
    } else { throw e; }
}

When it happens

Trigger: C# calls the native-element-hosting interop with an element id string that has not been registered/inserted into the DOM, or was already removed (e.g. element was detached during a visual-tree update before the interop call arrived).

Common situations: Element ID typo or mismatch between the C# managed HTML element wrapper and the DOM, element removed during a layout pass before retrieval, or the element was never attached (e.g. the hosting XAML element was never loaded into the visual tree).

Related errors

• retrieveFiles failed to find pending drag and drop data for
• Keyboard lock is not supported by this browser.
• Function ${funcName} returned an unsupported type: ${typeof
• A DragDropExtension has already been enabled
• The current DragDropExtension does not match the provided ar

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/0996a8b0db9a6898. Report an issue: GitHub.