You can use the methods defined in the Microsoft.Web.Administration namespace to query the MIME types from IIS programmatically.

C#:

    private void mp_ExtractMIMETypes()
    {
        using (ServerManager oServerManager = new ServerManager()) {
            Microsoft.Web.Administration.Configuration oConfiguration = oServerManager.GetApplicationHostConfiguration();
            Microsoft.Web.Administration.ConfigurationSection oStaticContent = oConfiguration.GetSection("system.webServer/staticContent");
            Microsoft.Web.Administration.ConfigurationElementCollection oMIMEMap = oStaticContent.GetCollection();
            foreach (Microsoft.Web.Administration.ConfigurationElement oMIMEEntry in oMIMEMap) {
                Debug.Print(oMIMEEntry.Item("fileExtension").ToString().ToLower() + "    " + oMIMEEntry.Item("mimeType"));
            }
        }
    }

Visual Basic .NET:

    Private Sub mp_ExtractMIMETypes()
        Using oServerManager As New ServerManager
            Dim oConfiguration As Microsoft.Web.Administration.Configuration = oServerManager.GetApplicationHostConfiguration()
            Dim oStaticContent As Microsoft.Web.Administration.ConfigurationSection = oConfiguration.GetSection("system.webServer/staticContent")
            Dim oMIMEMap As Microsoft.Web.Administration.ConfigurationElementCollection = oStaticContent.GetCollection()
            For Each oMIMEEntry As Microsoft.Web.Administration.ConfigurationElement In oMIMEMap
                Debug.Print(oMIMEEntry.Item("fileExtension").ToString().ToLower() & "    " & oMIMEEntry.Item("mimeType"))
            Next
        End Using
    End Sub

However you must include a reference to this dll in your project:

    %WinDir%\System32\InetSrv\Microsoft.Web.Administration.dll

And the project or assembly file must have administrator privileges.