用于Linq的去重 Distinct

/// <summary>

/// 用于Linq的去重,扩展方法需要放到静态类中

/// </summary>

/// <typeparam name="TSource"></typeparam>

/// <typeparam name="TKey"></typeparam>

/// <param name="source"></param>

/// <param name="keySelector"></param>

/// <returns></returns>

public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)

{

HashSet<TKey> seenKeys = new HashSet<TKey>();

foreach (TSource element in source)

{

if (seenKeys.Add(keySelector(element)))

{

yield return element;

}

调用方法：

list.DistinctBy(tmp => new { tmp.CountryName, tmp.VisaTypeName });

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