Use the Filters property of the FileDialog object to return a FileDialogFilters collection.
Use the Add method to add FileDialogFilter objects to the FileDialogFilters collection.
When changing the FileDialogFilters collection, remember that each application can only instantiate a single FileDialog object. This means that the FileDialogFilters collection will reset to its default filters whenever you call the FileDialog method with a new dialog box type.
Note A run-time error will occur if the Filters property is used in conjunction with the Clear, Add, or Delete methods when applied to a Save As FileDialog object.