将列表元素拼接成由分隔符分隔的字符串

列表操作扩展方法

最新推荐文章于 2024-04-14 19:00:00 发布

weixin_34260991

最新推荐文章于 2024-04-14 19:00:00 发布

阅读量261

点赞数

本文介绍两个实用的列表操作扩展方法：Montage用于将列表元素拼接成字符串，ToList则用于将泛型IEnumerable转换为泛型List，适用于C#开发者。

代码

public static class EnumerableExtension
{
    /// <summary>
    /// 将列表元素拼接成由splitter分隔的字符串
    /// </summary>
    /// <example>
    ///     拼接字符串：
    ///         <c>new List<string> { "aa", "bb", "cc" }.Montage(p => p, ","); // 返回："aa,bb,cc"</c>
    ///     拼接对象属性：
    ///         <c>new List<string> { "aa", "bbb", "c" }.Montage(p => p.Length.ToString(), ","); // 返回："2,3,1"</c>
    ///     拼接枚举值：
    ///         <c>new List<DomainType> { DomainType.GuanHao, DomainType.YaoJiKe }.Montage(p => ((int)p).ToString(), ","); // 返回："1,2"</c>
    ///     拼接枚举名：
    ///         <c>new List<DomainType> { DomainType.GuanHao, DomainType.YaoJiKe }.Montage(p => p.ToString(), ","); // 返回："GuanHao,YaoJiKe"</c>
    /// </example>
    /// <typeparam name="T"></typeparam>
    /// <param name="source"></param>
    /// <param name="toString">将列表元素转换为字符串的委托</param>
    /// <param name="splitter">分隔符（可为空）</param>
    /// <returns></returns>
    public static string Montage<T>(this IEnumerable<T> source, Func<T, string> toString, string splitter)
    {
        StringBuilder result = new StringBuilder();
        splitter = splitter ?? string.Empty;
        foreach (T item in source)
        {
            result.Append(toString(item));
            result.Append(splitter);
        }
        string resultStr = result.ToString();
        if (resultStr.EndsWith(splitter))
            resultStr = resultStr.Remove(resultStr.Length - splitter.Length, splitter.Length);
        return resultStr;
    }

    /// <summary>
    /// 从泛型IEnumerable创建一个泛型List，每个元素由converter进行类型转换。
    /// </summary>
    /// <example>
    ///     将枚举List转换为Int32 List：
    ///         <c>new DomainType[] { DomainType.GuanHao, DomainType.YaoJiKe }.ToList(p => (int)p); // 返回：List<int></c>
    /// </example>
    /// <typeparam name="TSource"></typeparam>
    /// <typeparam name="TResult"></typeparam>
    /// <param name="source"></param>
    /// <param name="converter"></param>
    /// <returns></returns>
    public static List<TResult> ToList<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> converter)
    {
        List<TResult> result = new List<TResult>();
        foreach (TSource item in source)
        {
            result.Add(converter(item));
        }
        return result;
    }
}