When a user clicks on Add Document, a File upload dialogue is displayed and the user browses for a file. Even though he clicks cancel button after file upload, workflow is triggering. How to avoid this behavior when user clicks on cancel button.
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You need to trigger the workflow on file modified, not file created.
Essentially, the process is: SharePoint uploads the file, then checks it out to the user who uploaded it until the required file metadata has been filled out, then update the file with the metadata.