public void Test_07_TestGetExtension( )
        {
            FileFilters filter = new FileFilters( );
            string filters = ( "Word (*.doc)|*.doc|WordX (*.docx)|*.docx||" );
            filter.PopulateCollections( filters );

            Assert.AreEqual( ".doc", filter.GetExtension( 0 ) );
            Assert.AreEqual( ".docx", filter.GetExtension( 1 ) );
            Assert.AreEqual( "should throw IndexOutOfRangeExctption", filter.GetExtension( 2 ) );
        }
        public void Test_06_TestCreateRegularExpression( )
        {
            FileFilters filter = new FileFilters( );
            string filters = ( "Documents (*.docx; *.doc)|*.docx; *.doc||" );
            filter.PopulateCollections( filters );

            filter.CreateRegularExpressions( );
            Regex regex = filter[ 0 ];
            Assert.AreEqual( @"(.+\.docx$)|(.+\.doc$)", regex.ToString( ) );
        }