Response.ContentType = "application/pdf" is Not working

I have the following code
If dr.Read() Then If CStr(dr("doc_name")).ToUpper.EndsWith(".PDF") Then Response.ContentType = "application/pdf" ElseIf CStr(dr("doc_name")).EndsWith(".htm") Or CStr(dr("doc_name")).EndsWith(".html") Then Response.ContentType = "text/html" ElseIf CStr(dr("doc_name")).EndsWith(".tif") Then Response.ContentType = "image/tiff" ElseIf CStr(dr("doc_name")).EndsWith(".jpeg") Or CStr(dr("doc_name")).EndsWith(".jpg") Then Response.ContentType = "image/jpeg" Else Response.ContentType = "application/msword" End If Response.Buffer = True ...