ASP.NET/IIS6: How to search the server's mime map?

Question

i want to find the mime-type for a given file extension on an IIS ASP.NET web-server from the code-behind file.

i want to search the same list that the server itself uses when serving up a file. This means that any mime types a web-server administrator has added to the Mime Map will be included.

i could blindly use

HKEY_CLASSES_ROOT\MIME\Database\Content Type

but that isn't documented as being the same list IIS uses, nor is it documented where the Mime Map is stored.

i could blindly call FindMimeFromData, but that isn't documented as being the same list IIS uses, nor can i guarantee that the IIS Mime Map will also be returned from that call.

Answer 1

Here's one I made earlier:

public static string GetMimeTypeFromExtension(string extension)
{
    using (DirectoryEntry mimeMap = 
           new DirectoryEntry("IIS://Localhost/MimeMap"))
    {
        PropertyValueCollection propValues = mimeMap.Properties["MimeMap"];

        foreach (object value in propValues)
        {
            IISOle.IISMimeType mimeType = (IISOle.IISMimeType)value;

            if (extension == mimeType.Extension)
            {
                return mimeType.MimeType;
            }
        }

        return null;

    }
}

Add a reference to System.DirectoryServices and a reference to Active DS IIS Namespace Provider under the COM tab. The extension needs to have the leading dot, i.e. .flv.

Answer 2

Here is another similar implementation, but doesn't require adding the COM reference - it retrieves the properties through reflection instead and stores them in a NameValueCollection for easy lookup:

using System.Collections.Specialized; //NameValueCollection
using System.DirectoryServices; //DirectoryEntry, PropertyValueCollection
using System.Reflection; //BindingFlags

NameValueCollection map = new NameValueCollection();
using (DirectoryEntry entry = new DirectoryEntry("IIS://localhost/MimeMap"))
{
  PropertyValueCollection properties = entry.Properties["MimeMap"];
  Type t = properties[0].GetType();

  foreach (object property in properties)
  {
    BindingFlags f = BindingFlags.GetProperty;
    string ext = t.InvokeMember("Extension", f, null, property, null) as String;
    string mime = t.InvokeMember("MimeType", f, null, property, null) as String;
    map.Add(ext, mime);
  }
}

You can very easily cache that lookup table, and then reference it later:

Response.ContentType = map[ext] ?? "binary/octet-stream";

Answer 3

IIS stores the MIME information in its own database. Searching for "MimeMap IIS" on the internet will reveal how to read it or even change it. See for example C# - How to display MimeMap entries to the console from an instance of IIS.