How to avoid save as dialogue box in mac?

Hi
I am showing pdf documents in my application using a menu, what i am doing is whenever a menu option is clicked for pdf file to view it calls a user control and in that user control i have made an iframe and that iframe calls a page called reference.aspx that calls the following code to show pdf file in that iframe.
MemoryStream Memory = new MemoryStream();
            FileStream file = null;
            Byte[] buffer = new Byte[10];
buffer = new Byte[file.Length];
            file.Read(buffer, 0, (int)file.Length);
            Memory.Write(buffer, 0, (int)file.Length);
            file.Close();

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