How to download/upload files from/to SharePoint 2013 using CSOM?

Question

I am developing a Win8 (WinRT, C#, XAML) client application (CSOM) that needs to download/upload files from/to SharePoint 2013.

How do I do the Download/Upload?

Answer 1

File.OpenBinaryDirect may cause exception when you are using Oauth accestoken Explained in This Article

Code should be written as below to avoid exceptions

 Uri filename = new Uri(filepath);
        string server = filename.AbsoluteUri.Replace(filename.AbsolutePath, 
         "");
        string serverrelative = filename.AbsolutePath;

        Microsoft.SharePoint.Client.File file = 
        this.ClientContext.Web.GetFileByServerRelativeUrl(serverrelative);
        this.ClientContext.Load(file);
        ClientResult streamResult = file.OpenBinaryStream();
        this.ClientContext.ExecuteQuery();
        return streamResult.Value;