使用C#使用lambda表达式过滤并添加值

C#新手，非常感谢您的帮助。问题是我需要根据数组（使用“allowedA”和“allowedB”数组）过滤api调用的结果。我不知道如何编辑lambda表达式来检查循环

 var activities = await _restClientTaxonomy.GetTaxonomyFullAsync(TAXONOMY_CLASSIFICATIONID_FOR_ACTIVITY);
 var activityTypes = await _restClientTaxonomy.GetTaxonomyFullAsync(TAXONOMY_CLASSIFICATIONID_FOR_ACTIVITY_TYPES);

            var documentEventxx = activities.Select(type => type.Id);

            long [] allowedA = new long []{ 7137, 40385637};
            long [] allowedB = new long []{ 7137, 40385637};


            foreach (long value in documentEventxx)
            {

                foreach (var item in allowed)
                {

                    if (item == value) {
                        //These are the values I am looking for -> values that are part of the documentEventxx and allowedB.
                    }
                }
            }

            var result = activityTypes.Select(type => new CategoryViewModel
            {
                Id = type.Id,//This is where I want to add only items that are in the allowedA array
                Text = type.Name,
                Types = activities.Where(a => a.ParentId == type.Id).Select(t => new TaxonomyMemberTextItem
                {
                    Id = t.Id, //This is where I want to add only items that are in the allowedB array
                    Text = t.Name
                }).ToList()
            }).ToArray();

我一直在阅读有关lambda表达式和foreach循环的文章，所以请不要只是发布一个随机链接

---

提前感谢。

要过滤，请使用

。Where

。您可以

。选择
创建新类型的列表。因此，为了进行筛选，然后创建所需对象的列表：

var result = activityTypes.Where(type=>isAllowed(type.Id)).Select(type => new CategoryViewModel
{
    Id = type.Id,//This is where I want to add only items that are in the allowedA array
    Text = type.Name,
    Types = activities.Where(a => a.ParentId == type.Id&&isAllowed(a.Id)).Select(t => new TaxonomyMemberTextItem
    {
        Id = t.Id, //This is where I want to add only items that are in the allowedB array
        Text = t.Name
    }).ToList()
}).ToArray();

在选择之前过滤这些值

            activityTypes.Where(x=>allowedA.Contains(x.Id)).Select(type => new CategoryViewModel
            {
                Id = type.Id,
                Text = type.Name,
                Types = activities.Where(a => a.ParentId == type.Id &&  allowedB.Contains(a.Id)).Select(t => new TaxonomyMemberTextItem
                {
                    Id = t.Id, 
                    Text = t.Name
                }).ToList()
            })

您是否尝试了活动。其中（a=>a.ParentId==type.Id&&allowedB.Contains（a.Id））？您可能需要使用IndexOf（a.id）更改.Contains（）-1，只需try.BTW，在选择TaxonomyMemberTextItem的地方，使用一个名为
t
的lambda变量，但它应该表示源类型，就像在它前面的where中一样，以便更具可读性，所以请尝试使用
a
。