检查CSV字符串是否包含给定值C#

我正在读取以逗号分隔的数字ID列表,该列表存储为字符串.我需要检查该列表中是否已存在id.例如:

"1,2,3"

如果我检查"2"我应该找到它,但如果我检查"22"我不应该.

什么是最直接,最简洁的方法？

我目前的代码如下:

HttpCookie cookie = Request.Cookies.Get("wishlist");
if (cookie != null)
{
     var JSONstring = cookie.Value; //Cookie stored as JSON
     Dictionary> jObj = JsonConvert.DeserializeObject>>(JSONstring); 

     // Retreive only the nodeId of each item and store it in a CSV list
     string umbracoCSV = String.Join(",", jObj.SelectMany(x => x.Value).Select(x => x.nodeId));

     // Convert the CSV into an IEnumerable list of ints
     IEnumerable umbracoNodeIdList = umbracoCSV.Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries).Select(int.Parse); 

     foreach(int umbracoNodeId in umbracoNodeIdList){
         if(umbracoNodeId == 2){
              // Do code if it matches
         }else{
              // Do code if it doesn't match
         }
     } 
}

正如您所看到的,此代码包含一个非常不必要的循环,我真的希望能够直接解析CSV字符串的值而不是执行嵌套循环(因为如果不可能,此循环将嵌套在另一个循环中).

任何帮助将不胜感激.