添加字符串列表，如果它不能找到

Question

我

List<List<string>> source 

包含例如

{{"a","b"},{"c","d"}} 

我也有一个

List<List<string>> target 

包含例如

{{"a","b"},{"e","f"}} 

什么是最简单的方法我可以得到在source无法找到target，被列入target？

这里{"c","d"}可以source被找到，但不target，因此分配后target应

{{"a","b"},{"e","f"},{"c","d"}} 

Answer 1

你可以使用LINQ：

target = source.Union(target).Distinct(new YourComparer()).ToList(); 

然后，你需要创建一个新的类它从IEqualityComparer继承而来（请参阅here以了解执行此操作的示例），它将执行所需的确切比较。

Answer 2

使用Linq.Union与自定义比较：

target = target.Union(source, new MyListComparer()) // Use the custom comparer to avoid duplication of the equal sequences. 
       .ToList(); 

随着相等比较器（如果你想有秩序独立的比较使用第二个选择在Equals功能）：

public class MyListComparer : IEqualityComparer<List<string>> 
{ 
    public bool Equals(List<string> x, List<string> y) 
    { 
     return x.SequenceEqual(y); // Use this if { "a", "b" } != { "a", "b" } 
     //return x.Count == y.Count && x.Count == x.Intersect(y).Count(); // Use this if { "a", "b" } == { "a", "b" } 
    } 

    public int GetHashCode(List<string> obj) 
    { 
     // GetHashCode is used to make the comparison faster by not comparing two elements that does not have the same hash code. 
     // GetHashCode must satisfy the following condition 
     // (x == y) implies (GetHashCode(x) == GetHashCode(y)) 
     // If your are extremely lazy, you can always return 0 but then the complexity of Union will be quadratic instead of linear. 
     return obj.Sum(item => item.GetHashCode()); 
    } 
}