c# - C#用对象区分两个列表

我有这两个列表result和resultNew：

data.AddMapping<Employee>(x => x.Name, "Name");
data.AddMapping<Employee>(x => x.Code, "Code");
data.AddMapping<Employee>(x => x.WorkingStatus, "Working Status");
var result = (from x in data.Worksheet<Employee>("Tradesmen")
              select x).ToList();


dataNew.AddMapping<Employee>(x => x.Name, "Name");
dataNew.AddMapping<Employee>(x => x.Code, "Code");
dataNew.AddMapping<Employee>(x => x.WorkingStatus, "Working Status");
var resultNew = (from x in dataNew.Worksheet<Employee>("On Leave")
                 select x).ToList();

其中，Employee是包含code，name和workingStatus字段的简单c＃代码

我想获取其code是resultNew而不是result中的数据

我尝试了这个：

var newEmployees = resultNew.Except(Code = result.Select(s => s.Code)).ToList();

但我收到语法错误：


  System.Collections.Generic.List'不包含'Except'的定义，最佳扩展方法重载'System.Linq.Enumerable.Except（System.Collections.Generic.IEnumerable，System.Collections.Generic.IEnumerable）'具有一些无效的论点

最佳答案

您可以为新员工的代码创建一个HashSet，然后按以下方式使用它：

HashSet<string> resultCodes = new HashSet<string>(result.Select(r => r.Code));
List<Employee> newEmployees = resultNew.Where(r => !resultCodes.Contains(r.Code))
                                    .ToList();

您还可以基于属性Equals为类Employee覆盖GetHashCode和Code，然后可以像下面这样使用Except：

class Employee
{
    protected bool Equals(Employee other)
    {
        return string.Equals(Code, other.Code);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != this.GetType()) return false;
        return Equals((Employee) obj);
    }

    public override int GetHashCode()
    {
        return (Code != null ? Code.GetHashCode() : 0);
    }

    public string Name { get; set; }
    public string Code { get; set; }
    public string WorkingStatus { get; set; }

}

然后：

var newEmployees = resultnew.Except(result).ToList();

请记住，上述Equals和GetHashCode的实现仅考虑Code属性。看到这个问题How do you implement GetHashCode for structure with two string, when both strings are interchangeable