How to post a file in an Ajax call to controller

Hi

I have a Main.cshtml which renders another partial view as below.

<div>@{Html.RenderPartial("FileUploadPopUp", Model.model1);}</div>

In the FileUploadPopup.cshtml as below I need to upload an Excel file.

<form><input type="file"><input type="button" value="Save" id="btnSave"></form>

In the Main.cshtml, I need to make an Ajax call to post the file as below.

$("#btnSave").click(function

() {  //Here need to make Ajax call to post the Excel file,

     //Could you please give me code how can I do it. 

}

Thank you,

Best regards,

Joseph