External Trigger

Trigger file selection from any button outside the uploader component.

What you should see: the uploader has no visible button of its own; the separate button on the page opens the file picker through the JS API. Useful when the trigger must live in a toolbar.

Drag & drop files here, or paste from clipboard

<core-upload id="externalTriggerUploader"
 asp-upload-url="/api/upload/upload"
 asp-multiple="true"
 asp-progress="true"
 asp-auto-upload="true">
</core-upload>

<button id="btn-external-browse">Browse Files (External)</button>

<script>
var uploader = CoreUpload.getInstance('#externalTriggerUploader');

document.getElementById('btn-external-browse')
 .addEventListener('click', function() {
 uploader.browse();
 });
</script>

Starting the upload from elsewhere

With asp-auto-upload="false" the queue waits, and anything on the page can start it — a form's submit handler, a wizard's next button, a toolbar rendered by a different component entirely.

Reaching the instance

CoreUpload.getInstance(idOrSelector) returns the uploader bound to a container, so the external trigger does not need a reference passed to it. That is what keeps the two halves of the page decoupled instead of threading an object between them.