c# - 在 LINQ 中使用求和方法

Question

我正在尝试对一个通用集合中的值求和，我在我的代码的其他部分中使用了完全相同的代码来执行此功能，但它似乎与ulong数据类型？

代码

   Items.Sum(e => e.Value); 

出现以下错误:

Error 15 The call is ambiguous between the following methods or properties: 'System.Linq.Enumerable.Sum<System.Collections.Generic.KeyValuePair<int,ulong>>(System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<int,ulong>>, System.Func<System.Collections.Generic.KeyValuePair<int,ulong>,float>)' and 'System.Linq.Enumerable.Sum<System.Collections.Generic.KeyValuePair<int,ulong>>(System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<int,ulong>>, System.Func<System.Collections.Generic.KeyValuePair<int,ulong>,decimal?>)

public class Teststuff : BaseContainer<int, ulong, ulong>
{
    public decimal CurrentTotal { get { return Items.Sum(e => e.Value); } }

    public override void Add(ulong item, int amount = 1)
    {
    }

    public override void Remove(ulong item, int amount = 1)
    {
    }
}

public abstract class BaseContainer<T, K, P>
{
    /// <summary>
    /// Pass in the owner of this container.
    /// </summary>
    public BaseContainer()
    {
        Items = new Dictionary<T, K>();
    }

    public BaseContainer()
    {
        Items = new Dictionary<T, K>();
    }

    public Dictionary<T, K> Items { get; private set; }
    public abstract void Add(P item, int amount = 1);
    public abstract void Remove(P item, int amount = 1);
}

Answer 1

Sum() 没有返回 ulong 的重载，编译器无法决定要调用哪些重载。

您可以通过强制转换帮助它做出决定:

Items.Sum(e => (decimal)e.Value)