为什么Lambda表达式返回System.Linq.Enumerable+WhereSelecteNumerableIterator`2作为结果

Question

在使用lambda表达式返回字符串列表时，我得到了以下字符串：

    IList<string> offerIds = new List<string>();
    foreach (var offer in offerProperties)
    {
       offerIds.Add(offer
         .Where(x => x.PropertyDefinitionId == propertyDefinitionId)
         .Select(x => x.OfferId)
         .ToString());
    }

null

和更多的建议。但没有答案对我有帮助。

有人知道这段代码出了什么问题吗？

Answer 1

而不是将序列转换为字符串:

 // How can .Net convert sequence into string? The only way is to return type name
 // which is unreadable System.Linq.Enumerable+WhereSelectEn... 
 offer
   .Where(x => x.PropertyDefinitionId == propertyDefinitionId)
   .Select(x => x.OfferId)
   .ToString()

将项连接到字符串中

  // Join items into string with "; " delimiter, e.g. "1; 2; 3; 4"
  offerIds.Add(string.Join("; ", offer
    .Where(x => x.PropertyDefinitionId == propertyDefinitionId)
    .Select(x => x.OfferId)));