使用lambda表达式查找两个列表之间的公共元素

本文关键字：之间 列表 元素 两个 表达式 lambda 查找 使用 | 更新日期: 2023-09-27 18:04:57

我有以下两个列表:

var firstList = new List<ProgramInfo> ()
{
    new ProgramInfo {Name = "A", ProgramId = 1, Description = "some text1"},
    new ProgramInfo {Name = "C", ProgramId = 2, Description = "some text2"},
    new ProgramInfo {Name = "D", ProgramId = 3, Description = "some text3"},
    new ProgramInfo {Name = "E", ProgramId = 4, Description = "some text4"}
};
var secondList = new List<ProgramInfo> ()
{
    new ProgramInfo {Name = "C", ProgramId = 2, Description = "some text1"},
    new ProgramInfo {Name = "D", ProgramId = 3, Description = "some text2"},
};

这两个列表是在运行时生成的我必须根据这两个列表中的程序id选择共同的ProgramInfo

例如，在上面的例子中，输出应该是 
var thirdList = new List<ProgramInfo>()
{
    new ProgramInfo {Name = "C", ProgramId = 2, Description = "some text1"},
    new ProgramInfo {Name = "D", ProgramId = 3, Description = "some text2"},
};
  public class ProgramInfo
  {
    public string Name { get; set; }
    public int ProgramId { get; set; }
    public string Description { get; set; }
  }

有人能建议我如何使用lambda表达式做到这一点吗?

使用lambda表达式查找两个列表之间的公共元素

使用Linq .Intersect。要做到这一点，你的类需要覆盖Equals和GetHashCode 

var thirdList = firstList.Intersect(secondList);

您也可以指定一个IEqualityComparer而不是覆盖函数:

public class Comparer : IEqualityComparer<ProgramInfo>
{
   public bool Equals(ProgramInfo x, ProgramInfo y)
   {
      return x.Name == y.Name &&
             x.ProgramId == y.ProgramId &&
             x.Description == y.Description;
   }
   public int GetHashCode(ProgramInfo obj)
   {
      return obj.Name.GetHashCode() ^
             obj.ProgramId.GetHashCode() ^
             obj.Description.GetHashCode();
   }
}
var thirdList = firstList.Intersect(secondList, new Comparer());
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