c# - C# 扩展方法中的 Lambda

Question

假设我想编写一个扩展方法来将一些数据从 T[,] 转储到 CSV:

public static void WriteCSVData<T>(this T[,] data, StreamWriter sw)
{
    for (int row = 0; row < data.GetLength(0); row++)
        for (int col = 0; col < data.GetLength(1); col++)
        {
            string s = data[row, col].ToString();

            if (s.Contains(","))
                sw.Write("\"" + s + "\"");
            else
                sw.Write(s);

            if (col < data.GetLength(1) - 1)
                sw.Write(",");
            else
                sw.WriteLine();
        }
}

我可以调用它

using (StreamWriter sw = new StreamWriter("data.csv"))
  myData.WriteCSVData(sw);

但是假设 myData 是一个 Complex[,] 并且我想写复数的大小，而不是完整的值。如果我能写的话会很方便:

using (StreamWriter sw = new StreamWriter("data.csv"))
  myData.WriteCSVData(sw, d => d.Magnitude);

但我不确定如何在扩展方法中实现它，或者它是否可能。

Answer 1

您可以像这样重载现有方法:

public static void WriteCSVData<T, TValue>(this T[,] data, StreamWriter sw, 
    Func<T,TValue> func)
{
    for (int row = 0; row < data.GetLength(0); row++)
        for (int col = 0; col < data.GetLength(1); col++)
        {
            string s = func(data[row, col]).ToString();

            if (s.Contains(","))
                sw.Write("\"" + s + "\"");
            else
                sw.Write(s);

            if (col < data.GetLength(1) - 1)
                sw.Write(",");
            else
                sw.WriteLine();
        }
}

并按照您想要的方式使用它:

using (StreamWriter sw = new StreamWriter("data.csv"))
    myData.WriteCSVData(sw, d => d.Magnitude);