c# – 使用带有种子的LINQ Aggregate,Resharper声明表达式始终为false

2023年4月1日 180次阅读

在以下代码中,Resharper声称表达式currMax == null始终为false.

public Read Read1
{
    get
    {
        return Reads.Where(read => !read.IsIndex)
                    .Aggregate((Read)null, (currMax, read) => currMax == null || read.Length > currMax.Length ? read : currMax);
    }
}

当对Aggregate的调用中的lambda表达式的第一次迭代执行时,我希望currMax == null为真,因为(Read)null是种子. Resharper知道上游Where在生成的IEnumerable中需要非空的Read对象,因为我正在访问Read类的IsIndex属性. resharper只是不考虑Aggregate的种子参数吗？

编辑：我在这里提交了一份错误报告https://youtrack.jetbrains.com/issue/RSRP-443055

最佳答案 看起来ReSharper是错误的,从ILSpy中的Aggregate的反汇编来看.

public static TAccumulate Aggregate<TSource, TAccumulate>(
    this IEnumerable<TSource> source, 
    TAccumulate seed, 
    Func<TAccumulate, TSource, TAccumulate> func)
{
    if (source == null)
    {
        throw Error.ArgumentNull("source");
    }
    if (func == null)
    {
        throw Error.ArgumentNull("func");
    }
    TAccumulate tAccumulate = seed;
    foreach (TSource current in source)
    {
        tAccumulate = func(tAccumulate, current);
    }
    return tAccumulate;
}

清除删除空检查将导致空引用异常.

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