SharePoint. Getting Document Icon URL

docicon.xml

All the icons for files on SharePoint are registered in the file, located at \14\TEMPLATE\XML\DOCICON.XML. Here is a small piece of it:

<?xml version="1.0" encoding="utf-8"?>
<DocIcons>
    <ByProgID>
        <Mapping Key="Excel.Sheet" Value="ichtmxls.gif" EditText="Microsoft Excel" />
    <!-- ... -->
    </ByProgID>
    <ByExtension>
        <Mapping Key="zip" Value="iczip.gif" OpenControl=""/>
        <!-- ... -->
    </ByExtension>
    <Default>
        <Mapping Value="icgen.gif"/>
    </Default>
</DocIcons>

To read this data here is a static class:

/// <summary>
/// Document icons from DOCICON.XML file
/// </summary>
public static class DocumentIcons
{
    private static NameValueCollection ExtensionImages { get; set; }
 
    static DocumentIcons()
    {
        ExtensionImages = new NameValueCollection();
        // Path to docicon.xml file
        var dociconPath = SPUtility.GetGenericSetupPath(@"template\xml") + @"\docicon.xml";
        var fi = new FileInfo(dociconPath);
        using (var stream = fi.OpenText())
        {
            var doc = XDocument.Load(stream);
            var icons = doc.Element("DocIcons");
            var byExt = icons.Element("ByExtension");
            foreach (var ext in byExt.Elements())
            {
                var key = ext.Attribute("Key").Value;
                var val = ext.Attribute("Value").Value;
                ExtensionImages.Add(key, "/_layouts/images/" + val);
            }
        }
    }
 
    /// <summary>
    /// Getting document icon URL by file extension
    /// </summary>
    /// <param name="extension">Extension without dot</param>
    /// <returns>URL of icon</returns>
    public static string GetIconUrl(string extension)
    {
        return ExtensionImages[extension] ?? "/_layouts/images/ICGEN.GIF";
    }
}

You can use it, for example, by creating a property in your class representing any document like this:

/// <summary>
/// Icon URL
/// </summary>
public string IconUrl
{
    get
    {
        // Get file extension
        var ext = System.IO.Path.GetExtension(ServerUrl);
        if (ext.Length > 0)
        {
            // Cut off leading dot
            ext = ext.Substring(1);
            // Return icon&for extension
            return DocumentIcons.GetIconUrl(ext);
        }
        // Return default icon
        return DocumentIcons.GetIconUrl(string.Empty);
    }
}