如何制作一个遍历列表并以要访问的数据成员作为输入参数的函数

Question

I have a datatype PlayerStats which contains a lot of different data members. I want to calculate a score which is different for each data member (the case below looks at statistics.nrOfGoals).

private double getScore()
{
    double strength = 0;
    foreach (PlayerStats statistics in this.statistics)
    {
        double dateDiff = Math.Abs(nowDate.Subtract(statistics.date).Days / (365.25 / 12));
        dateDiff = Math.Pow(dateDiff, Form1.historyFactor);

        strength += (statistics.nrOfGoals * ValueTable.PointsPerGoals   ) / dateDiff;
    }

    return strength;
}

How can I make this function general and accept which datamember to look at instead of creating a lot of similar looking functions?

Something like

private double getScore(Type type, Type type2)
{
    double strength = 0;
    foreach (PlayerStats statistics in this.statistics)
    {
        double dateDiff = Math.Abs(nowDate.Subtract(statistics.date).Days / (365.25 / 12));
        dateDiff = Math.Pow(dateDiff, Form1.historyFactor);

        strength += (statistics.type * ValueTable.type2) / dateDiff;
    }

    return strength;
}

Answer 1

You can give a function as a parameter with signature PlayerStats -> Double :

private double getScore(Func<PlayerStats,double> type, double type2)
{
    double strength = 0;
    foreach (PlayerStats statistics in this.statistics)
    {
        double dateDiff = Math.Abs(nowDate.Subtract(statistics.date).Days / (365.25 / 12));
        dateDiff = Math.Pow(dateDiff, Form1.historyFactor);

        strength += (type(statistics) * type2) / dateDiff;
    }

    return strength;
}

And then call it with:

getScore(x => x.nrOfGoals,ValueTable.PointsPerGoals);

x => x.nrOfGoals is a lambda-expression that defines some kind of function that (in this case) takes as input a PlayerStats instance and returns a double .

In the code, you can then see type as a "function"/"method" and call it with type(y) (with y a PlayerStats instance).

Answer 2

您可以将属性名称作为字符串参数，并使用反射按名称查找属性。

Answer 3

You can pass Func<PlayerStats, double> to your function, like:

private double getScore(Func<PlayerStats, double> evaluator)
{
    double strength = 0;
    foreach (PlayerStats statistics in this.statistics)
    {
        double dateDiff = Math.Abs(nowDate.Subtract(statistics.date).Days / (365.25 / 12));
        dateDiff = Math.Pow(dateDiff, Form1.historyFactor);

        strength += evaluator(statistics) / dateDiff;
    }

    return strength;
}

And then call it like (in your shown case)

getScore(x => x.nrOfGoals * ValueTable.PointsPerGoals);