I am developing a web application that manages a population of plants. One feature of the application is the ability to view relationships between plants as a graph. This visualisation is generated as a dot file, then turned into SVG using GraphViz. The resulting SVG markup is then rendered to the browser via an .aspx file, using the Response.Write() technique.

Aspx markup:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Visualisation.aspx.cs" Inherits="Webapp.PopulationManager.Visualisation" %>

Codebehind:

protected void Page_Load(object sender, EventArgs e)
    {
        if(!Page.IsPostBack)
        {
            // ...snip...
            string svgString = PopulationModule.VisualiseTable(connectionTable, title, url.ToString());

            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.ContentType = "image/svg-xml";
            Response.AddHeader("Content-Disposition", string.Format("inline;filename={0}", filename));
            Response.Write(svgString);
            Response.Flush();
        }
    }

This techniques works perfectly on my Windows development machine (a dialog pops up asking me to save/open the SVG file).

However it fails when deployed to the Linux server that is hosting this app - the page returns the SVG markup, but a garbage string of about 5-6 characters is added as the first line, causing the browser to fail parsing the SVG file.

The Linux host runs RHEL5, Mono 1.9, and Lighttpd (with fast-cgi to talk to Mono).

I have verified that the SVG markup is generated cleanly on the Linux server; and if I run the web app with XSP2 instead of Lighttpd, the page works as expected. The garbage line is added somewhere after the SVG markup is generated (so I can t simply remove the first line before writing out the response).

Does anyone know what might be causing this? Options, ideas, and thoughts greatly recieved!

Thanks.

EDIT:

The characters vary depending on the entity I create a visualisation for - but remain the same for a given entity. So if I create an SVG visualtion for object A, I ll always get the string 1f35 as garbage in the first line.