Remove list from a list in C# based on specific condition

Question

I want to remove objects of one list that are present on other list according to condition here are my two lists

List Structure

list1 = {GuideId ,Text , Desc , SecId , NextBtnText , ParentId}

list2 = {userId , ParentId , GuideId , Status }

data for list one

list1[0]{GuideId = 1 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list1[1]{GuideId = 2 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list1[2]{GuideId = 3 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list1[3]{GuideId = 4 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list1[4]{GuideId = 5 , Text=abc , Desc=any , SecId =2 , ParentId = 2} 

data for list 2

list2[0]{GuideId = 1 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list2[1]{GuideId = 2 , Text=abc , Desc=any , SecId =2 , ParentId = 2}

list2[2]{GuideId = 3 , Text=abc , Desc=any , SecId =2 , ParentId = 2} 

these data come from db it may be thousand

but I need where GuideId matches it would remove the data from list

what I applied is not working

Here is the code

List1 = List1.Except(List2).ToList();

Here is my Code

  userGuideList = query.ToList<GuidedPopupsViewModel>();
     popUpGuideListVm = query2.ToList<GuidedPopupsViewModel>();
    popUpGuideListVm = popUpGuideListVm.Except(userGuideList).ToList();

Answer 1

That doesn't work because Except doesn't know how you want to compare the objects. So it just compares references. You have to override Equals + GetHashCode or you have to provide a custom IEqualityComparer<T> .

But you could also use List.RemoveAll instead:

List1.RemoveAll(x=> List2.Any(x2 => x2.GuideId == x.GuideId));

Answer 2

您可以尝试根据GuideId删除

List2.Where(x => !List1.Select(y => y.GuideId).Contains(x.GuideId))

Answer 3

另一种方法是在linq中使用foreach，此方法仅比较ID，无需覆盖或引用相等：

list2.ForEach(x => list.RemoveAll(y => y.GuidId == x.GuidId));