Question

我的程序将坐标（double x，douule y）读入ListBox，需要在使用SelectedIndices和MultiExtended选择它们后计算它们的平均值。问题是如何使用每个Multiselection刷新我的代码。如您所见，我将SelectedIndices [0]设置为默认值为0。目前我的程序只是将第一个坐标的平均值除以selectedIndices的数量。

如果您考虑改进我的代码的任何方法，我也想知道。

谢谢！

   private void button3_Click(object sender, EventArgs e)//Average
    {
        int[] selected = new int[] {points_List.SelectedIndices[0] };
        double sumX = 0, sumY = 0; ;
        foreach (int iIndex in selected)
        {
            sumX += points[iIndex].X;
            sumY += points[iIndex].Y;
        }
        averageX = (sumX) / (points_List.SelectedIndices.Count);
        averageY = (sumY) / (points_List.SelectedIndices.Count);
        label1.Text = "Average is: ";
        label1.Text += averageX.ToString();
        label1.Text += "   ";
        label1.Text += averageY.ToString();
    }

Answer 1

正确的代码需要SelectedIndices到OfType<T>或Cast<T>。此外，调用ToArray来实现结果是很方便的，以避免必须计算两次。

var selectedPoints = points_List.SelectedIndices.
    OfType<int>().
    Select(i => points[i]).
    ToArray();
var averageX = selectedPoints.Average(p => p.X);
var averageY = selectedPoints.Average(p => p.Y);

Answer 2

最终解决方案，谢谢大家。

        {
        double averageX = 0, averageY = 0;
        var selectedPoints = from int i in pointsList.SelectedIndices select points[i];
        if (pointsList.SelectedIndices.Count == 0)
        {
            label1.Text = "Average is 0.000 0.000 ";//default text
            return;
        }
        averageX = selectedPoints.Average(p => p.X);
        averageY = selectedPoints.Average(p => p.Y);
        label1.Text = "Average X: ";
        label1.Text += averageX.ToString();
        label1.Text += "   Y:";
        label1.Text += averageY.ToString();
    }

使用SelectedIndices计算平均值

2 个答案: