How to download file on .NET OWIN

Sometimes we need to use browser navigation or iframe mechanism to download file as some old browsers don’t support html5 file API. But there’s a problem that most of applications has access control, thus you can’t access the server source directly.

How to do it on .NET OWIN?

My solution is to append access token to parameters of http request, then parse the token and wrap it to header of http request on the server-side. The code snippet in the StartUp.Auth.cs

app.Use(async (context, next) =>
{
    if (context.Request.QueryString.HasValue)
    {
        if (string.IsNullOrWhiteSpace(context.Request.Headers.Get("Authorization")))
        {
            var queryString = HttpUtility.ParseQueryString(context.Request.QueryString.Value);
            string token = queryString.Get("accessToken");
            if (!string.IsNullOrWhiteSpace(token))
            {
                context.Request.Headers.Add("Authorization", new[] { string.Format("Bearer {0}", token) });
            }
        }
    }
    await next.Invoke();
});