How to upload an image from local PC then assign it to a property type "Image"

I'm build an external .net tool using IOM dll. I have an item type "Company" contains a property type Image named "Picture", and in order to import data for Company I would like to upload an image from Local PC then set the uploaded one to Picture. I know that the behavior looks like "Select an image..." browser in ARAS Innovator, but I can't find the methods to do that. I have tried to upload a image to File Handing->Files first, then get its id, get the file item by this id and assign to Company but it doesn't work properly, example code:

Item company = inn.new("Company", "add"); // create new company Item file = Innovator.newItem("File", "get"); // get the file with id file.setID("Id of the image"); file = file.apply(); if(file.isError()) { return false; } company.setPropertyItem("Picture", file);  

Any idea? Thanks in advanced.