How to determin if a file uploaded in multiple type situation?

[simpsonyang]

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Content

1. I'd like to use the file upload feature in version 0.10.0, I want to upload one file at a time but can be doc or image.
2. In the workflow, I will check if there is no file been uploaded, then go way 1.
3. If the file type is doc, then go way 2, else if the file type is image, then go way 3.
   The problem is, if I set "file upload" to single file, then I can use "if node" for step 2, but can not use "list operator" in step 3. If I set "file upload" to file list, then I can only use "list operator" node for file type, but cannot determin if the file exists.
   Pls help.

[simpsonyang]

I am wrong. There are two "upload files", one in start node, the other in dialog.