C# Flags特性的使用案例

现在有这么一个需求：

生成随机长度的一个字符串，要求可以包含大写字母或者小写字母，或者数字，这三种排列组合都可以

效果如下

后台代码

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace MvvmToolkit学习
{
    /// <summary>
    /// 字符类型
    /// </summary>
    [Flags]
    public enum CharacterType
    {
        /// <summary>
        /// 无内容
        /// </summary>
        None = 0,

        /// <summary>
        /// 小写字母
        /// </summary>
        LowercaseEnglish = 1,

        /// <summary>
        /// 大写字母
        /// </summary>
        UppercaseEnglish = 2,

        /// <summary>
        /// 数字
        /// </summary>
        Number = 4,
    }

    public class SelectItem
    {
        public CharacterType CharacterType { get; set; }
        public bool IsSelected { get; set; }
    }

    /// <summary>
    /// RandomCharacter.xaml 的交互逻辑
    /// </summary>
    public partial class RandomCharacter : Window
    {
        /// <summary>
        /// 小写英文字符
        /// </summary>
        public const string LowercaseEnglishCharacters = "abcdefghijklmnopqrstuvwxyz";

        /// <summary>
        /// 数字字符
        /// </summary>
        public const string NumberCharacters = "0123456789";

        /// <summary>
        /// 大写英文字符
        /// </summary>
        public const string UppercaseEnglishCharacters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        private ObservableCollection<SelectItem> SelectItems { get; set; }

        public RandomCharacter()
        {
            InitializeComponent();
            //填入数据
            SelectItems = new ObservableCollection<SelectItem>();
            var list = Enum.GetNames(typeof(CharacterType))
                .Select(e => new SelectItem() { CharacterType = (CharacterType)Enum.Parse(typeof(CharacterType), e), IsSelected = true });
            EnumTypeListBox.ItemsSource = SelectItems;
            foreach (var item in list)
            {
                SelectItems.Add(item);
            }
        }

        /// <summary>
        /// 随机字符串
        /// </summary>
        /// <param name="length">字符串长度</param>
        /// <param name="characterType">组成字符串的字符类型</param>
        /// <returns></returns>
        /// <exception cref="ArgumentException"></exception>
        public static string GenerateRandomCharacters(int length, CharacterType characterType)
        {
            var list = new List<char>();

            if (characterType == CharacterType.None)
            {
                throw new ArgumentException("参数错误");
            }
            //判断传入的参数是否包含特定枚举
            if (characterType.HasFlag(CharacterType.LowercaseEnglish))
            {
                list.AddRange(LowercaseEnglishCharacters.ToList());
            }
            if (characterType.HasFlag(CharacterType.UppercaseEnglish))
            {
                list.AddRange(UppercaseEnglishCharacters.ToList());
            }
            if (characterType.HasFlag(CharacterType.Number))
            {
                list.AddRange(NumberCharacters.ToList());
            }

            var builder = new StringBuilder();
            var random = new Random();
            for (int i = 0; i < length; i++)
            {
                var index = random.Next(list.Count);
                builder.Append(list[index]);
            }
            return builder.ToString();
        }

        private void Generate(object sender, RoutedEventArgs e)
        {
            //获取所有选择的类型
            var values = SelectItems.Where(s => s.IsSelected)
                .Select(s => s.CharacterType)
                .Aggregate((x, y) => x | y);

            DisplayTextBlock.Text = GenerateRandomCharacters(10, values);
        }
    }

  
}

界面代码

<Window
    x:Class="MvvmToolkit学习.RandomCharacter"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:MvvmToolkit学习"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="RandomCharacter"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <Grid>
        <StackPanel Orientation="Vertical">
            <ListBox
                DataContext="{Binding SelectItems}"
                x:Name="EnumTypeListBox"
                Width="200">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <CheckBox IsChecked="{Binding IsSelected}" Content="{Binding CharacterType}"/>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
            <TextBlock
                x:Name="DisplayTextBlock"
                FontSize="20"
                HorizontalAlignment="Center"
                VerticalAlignment="Center"
                Foreground="Red"
                Width="200"
                Height="50"/>
            <Button
                Width="200"
                Height="50"
                Click="Generate"/>
        </StackPanel>
    </Grid>
</Window>

看起来简单又方便