jquery / javascript for upload the file from browser to server

I am developing the application in asp.net mvc with c#. I want the functionality that , a div will popup,开发者_如何学Python so that i can facilate to use to upload the image file from his browser to server , in application domains file system. as usual. This question may be repeat , but i expect something more like

1. how to build this scenario, and what are the security issues may come?
2. and what care have to take while coding in the security perspective ?

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Yes you can ask multiple questions in 'step-by-step' format