IIS MIME Settings Inheritance in C#

I'm trying to set a MIME type for a certain file extension (.jdf) using MimeMapClass in C#.

Following is the code I use which works fine.

Code:

---

        // directory is a virtual directory, say BSS
        // extension = ".jdf"
        // type = "text/xml"
        private static void SetMIMEType(DirectoryEntry directory, string extension, string type)
        {
            bool MIMETypeExists = false;
           
            //Retrieve the MimeMap of [directory]
            PropertyValueCollection propertyValues = directory.Properties["MimeMap"];
            if (propertyValues.Count > 0)
            {
                //Check if the MIME type already exists in the directory
                foreach (object obj in propertyValues)
                {
                    if (((IISMimeType)obj).Extension == extension)
                    {
                        MIMETypeExists = true;
                        break;
                    }
                }
            }

            //If the MIME type does not exist, it is added to the MIME map of [directory]
            if (MIMETypeExists == false)
            {
                MimeMapClass tempMIMEObj = new MimeMapClass();
                tempMIMEObj.Extension = extension;
                tempMIMEObj.MimeType = type;
                directory.Properties["MimeMap"].Add(tempMIMEObj);
            }
        }

---

What it does is, retieve the MimeMap of [directory] which is a Virtual Directory listed under [Default Web Site] in my IIS Manager. Now it works fine under usual circumstances. However, a problem arises when my [directory], let's call it BSS, inherits the file extention (.jdf) to which I try
to set MIME type from above.

Let me elaborate more. Here is my file structure in IIS Manager.

[ComputerName\User]
|
|
Site
|
|
Default Web Site
|
|
BSS

Now I manually add a MIME type to the file extension [.jdf] in, say, [Default Web Site]. When I do
that my IIS Manager automatically inherits this extension and it's value to BSS from Defult Web Site. However, if I run my code sample now it does not know this and still tries to register a MIME
type for the same extension which causes an error.

How can I know from within C# that if the folder to which I'm trying to set a MIME type has already inherited the said file extension from a folder above (be it Default Web Site or anything
above either)?