produproperty.ViewModel.viewModel.file_open C# (CSharp) Method

        public async void file_open()
        {
            FileOpenPicker pick = new FileOpenPicker();
            //显示方式
            pick.ViewMode = PickerViewMode.Thumbnail;
            //选择最先的位置
            pick.SuggestedStartLocation =
                PickerLocationId.PicturesLibrary;
            //后缀名
            pick.FileTypeFilter.Add(".txt");
            pick.FileTypeFilter.Add(".md");

            StorageFile file = await pick.PickSingleFileAsync();

            if (file != null)
            {
                _m.open_file(file);
            }
        }