Get Mime Type from IIS

Except the System.DirectoryServices, I also need to add a reference of com object "Active DS IIS Namespace Provider" in VS.

using System.DirectoryServices;

public static string GetMimeType(string extension)
{
string retMimeType = null;

using (DirectoryEntry mimeMap = new DirectoryEntry("IIS://Localhost/MimeMap"))
{
PropertyValueCollection pValues = mimeMap.Properties["MimeMap"];

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

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

}
return retMimeType;
}