/// <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 });