c# - 并非所有代码路径都返回 'System.Func' 类型的 lambda 表达式中的值

Question

这个问题在这里已经有了答案:





Lambda expression returning error

(4 个回答)


7年前关闭。




我正在创建一个调用函数 CountPixels 的任务，如下所示

Task<int> task1 = new Task<int>(()=>{CountPixels(croppedBitmap, Color.FromArgb(255, 255, 255, 255));});

CountPixels的代码如下:

private int CountPixels(Bitmap croppedBitmap, Color target_color)
    {
        int height = croppedBitmap.Height;
        int width = croppedBitmap.Width;
        int matches = 0;
        List<int> x1range = new List<int>();
        List<int> y1range = new List<int>();
        for (int y1 = 0; y1 < height; y1++)
        {
            for (int x1 = 0; x1 < width; x1++)
            {
                if (croppedBitmap.GetPixel(x1, y1) == target_color
                {
                    matches++;
                    x1range.Add(x1);
                    y1range.Add(y1);
                }
            }
        }
        Console.WriteLine("before modification : {0} ms", sw.ElapsedMilliseconds);
        x1range.sort;
        y1range.sort;
        int x1max, y1max;
        x1max = x1range.Count - 1;
        y1max = y1range.Count - 1;
        try
        {
            fruit1.Text = "X1 MIN =  " + x1range[0] + "  X1 MAX =  " + x1range[x1max] + "  Y1 MIN =  " + y1range[0] + "  Y1 MAX =  " + y1range[y1max];
        }
        catch (Exception ex)
        {
            MessageBox.Show("" + ex);
        }
        return matches;
    }

我在 task1 行收到错误:

Not all code paths return a value in lambda expression of type 'System.Func int>'

请帮帮我..我哪里错了？
谢谢!

Answer 1

这很简单。不要忘记返回值:

Task<int> task1 = new Task<int>(()=> { return CountPixels(croppedBitmap, Color.FromArgb(255, 255, 255, 255)); });