how to extract the content type and filename type to save a file

hi,,,look at my code
Response.ContentType = "application/ms-word";
Response.AddHeader("content-disposition", "attachment; filename=Worddocument.doc");
FileStream sourceFile = new FileStream(path, FileMode.Open);
long FileSize;
FileSize = sourceFile.Length;
byte[] getContent = new byte[(int)FileSize];
sourceFile.Read(getContent, 0, (int)sourceFile.Length);
sourceFile.Close();
Response.BinaryWrite(getContent);
dis is used to save a word type document file,,,how can i make it general so dat i can get any file extension...i think i need to use some eval expression to get the type of filename....

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