c# - 无法从 IEnumerable 转换为“System.Collections.Generic.IEqualityComparer

Question

您好，我有如下代码。尝试从列表中获取“UnitNo”属性时出现错误:无法从“System.Collections.Generic.IEnumerable>”转换为“System.Collections.Generic.IEqualityComparer”

public class UnitSyncModelSchema
{
    public ICollection<UnitBedRequest> UnitBeds { get; set; }
}

public class UnitBedRequest
{
    public string UnitNo { get; set; }
}

public static List<UnitSyncModelSchema> GetUnitById()
{
    ....
    return List<UnitSyncModelSchema>;
}

static int Main(string[] args)
{
    List<UnitSyncModelSchema> units = GetUnitById();

    //got error on this line
    var UnitNo = new HashSet<string>(vesUnits.Select(s1 => s1.UnitBeds.Select(s2 => s2.UnitNo)));
}

Answer 1

您需要 SelectMany 而不是 Select 因为 UnitBeds 是一个集合:

var UnitNo = new HashSet<string>(vesUnits.SelectMany(s1 => s1.UnitBeds.Select(s2 => s2.UnitNo)));