两个c#列表都被修改

Question

我的两个列表都被修改,我试图避免这种行为......

这里有什么问题？

我有一个'大'列表,我想删除itemsToRemoveList中存在的所有项目,但没有修改原始列表.

我简化了示例代码..

List<string> aList = new List<string>(){"My","name","is", "jeff"}; // cached full list

List<string> bList = aList; // initial copy

List<string> itemsToRemoveList = new List<string>(){"jeff"};

bList.RemoveAll(itemsToRemoveList.Contains); // remove only from copy

foreach (string s in aList)
{
    Console.Write(s + " "); // expect "my name is jeff"
}
Console.WriteLine();
foreach (string s in bList)
{
    Console.Write(s + " "); // expect "my name is"
}
// however this modifies both collections. 

        Console.ReadLine();

Answer 1

当你这样做

List<string> bList = aList;

那不是创建新列表.它只是将您的bList变量设置为指向同一列表的引用aList.制作副本的方法是实际创建一个新列表.

List<string> bList = new List<string>(aList);

但如果您还想过滤值,最好使用Linq.

List<string> aList = new List<string>(){"My","name","is", "jeff"}; 
List<string> itemsToRemoveList = new List<string>(){"jeff"};
List<string> bList = aList.Where(a => !itemsToRemoveList.Contains(a)).ToList(); 

foreach (string s in aList)
{
    Console.Write(s + " "); 
}
Console.WriteLine();
foreach (string s in bList)
{
    Console.Write(s + " "); 
}