c# - 无法将 void 分配给隐式类型的局部变量

Question

var query = rep.GetIp()  // in this line i have the error
           .Where(x => x.CITY == CITY)
           .GroupBy(y => o.Fam)
           .Select(z => new IpDTO
                        {
                            IId = z.Key.Id,
                            IP = z.Select(x => x.IP).Distinct()
                        })
           .ToList().ForEach(IpObj => IpObj.IP.ToList().ForEach(ip => PAINTIP(ip)));

当我运行这段代码时出现错误:

Cannot assign void to an implicitly-typed local variable

我谷歌了一下，发现这是一个类型问题，因为 foreach 不是 LINQ 函数？我不明白 void 在哪里!

Answer 1

• ForEach()类型为 void .

• Select()返回 IEnumerable<T> , ToList()返回 List<T>等

所以:

List<X> x = ...Select(x => x).ToList(); // List<T>

或

x.ForEach(x => x); // void

因为你不能分配 void至 List<T> .

---

var query = rep.GetIp()  // in this line i have the error
           .Where(x => x.CITY == CITY)
           .GroupBy(y => o.Fam)
           .Select(z => new IpDTO
                        {
                            IId = z.Key.Id,
                            IP = z.Select(x => x.IP).Distinct()
                        });

foreach (var dto in query)
{
    foreach (var ip in dto.IP)
    {
        PAINTIP(ip);
    }
}

或

var query = ....
           .SelectMany(z => z.Select(x => x.IP).Distinct());

foreach (var ip in query)
{
    PAINTIP(ip);
}