基于列取两个列表的并集

本文关键字：列表 两个 于列取 | 更新日期: 2023-09-27 18:17:52

我正在使用Linq to Sql进行两个列表的联合。使用List1和List2:

 var tr = List1.Union(List2).ToList();

Union工作得很好，但问题是它检查每一列并删除我想要的一些行。所以我想知道是否有一种方法可以只基于一列执行并集，比如每个列表的id ?

类似:

var t = List1.id.Union(List2.id).ToList();

这不起作用，但我想知道是否有一种方法可以做到这一点，无论是用LINQ还是T-SQL

基于列取两个列表的并集

你应该使用这个Union()重载(带有一个自定义的相等比较器)，或者类似这样的东西:

list1.Concat(list2).GroupBy(x => x.DateProperty).Select(m => m.First());

当然，您需要一个带有Union的自定义IEqualityComparer。我有一个非常动态的，很大的代码块传入:

public class PropertyEqualityComparer<TObject, TProperty> 
    : IEqualityComparer<TObject>
{
    Func<TObject, TProperty> _selector;
    IEqualityComparer<TProperty> _internalComparer;
    public PropertyEqualityComparer(Func<TObject, TProperty> propertySelector,
        IEqualityComparer<TProperty> innerEqualityComparer = null)
    {
        _selector = propertySelector;
        _internalComparer = innerEqualityComparer;
    }
    public int GetHashCode(TObject obj)
    {
        return _selector(obj).GetHashCode();
    }
    public bool Equals(TObject x, TObject y)
    {
        IEqualityComparer<TProperty> comparer = 
            _internalComparer ?? EqualityComparer<TProperty>.Default;
        return comparer.Equals(_selector(x), _selector(y));
    }
}
public static class PropertyEqualityComparer
{
    public static PropertyEqualityComparer<TObject, TProperty>
        GetNew<TObject, TProperty>(Func<TObject, TProperty> propertySelector)
    { 
        return new PropertyEqualityComparer<TObject, TProperty>
            (propertySelector);
    }
    public static PropertyEqualityComparer<TObject, TProperty>
        GetNew<TObject, TProperty>
        (Func<TObject, TProperty> propertySelector, 
        IEqualityComparer<TProperty> comparer)
    { 
        return new PropertyEqualityComparer<TObject, TProperty>
            (propertySelector, comparer);
    }
}

现在，您需要做的就是使用相等比较器调用Union(使用适合您的情况的lambda实例化):

var tr = List1.Union(List2, PropertyEqualityComparer.GetNew(n => n.Id)).ToList();

try something this

var List3 = List1.Join(
List2, 
l1 => l1.Id,
l2 => l2.Id,
(l1, l2) => new Model
{
   Id = l1.Id,
   Val1 = l1.Val1 or other,
   Val2 = l2.Val2  or other
});

更多细节，你可以显示你的模型

试试这个:

var merged = new List<Person>(list1);
merged.AddRange(list2.Where(p2 => 
                list1.All(p1 => p1.Id != p2.Id)));
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