这句语句是放在一个循环里面的，源代码是：

for (int i = 0; i < gen; i++)
{
g.DrawLine(myPen, 3, 103, 6, 106);
}
搞笑的是，同样是画线，第一次循环i=0时运行正常，第二次循环i=1时总报错说参数无效。。。明明参数是常数。。。想不通

其它代码我想应该没什么问题的。。。贴一下
for (int i = 0; i < gen_GA-1; i++)
{
//绘制进化曲线
Pen myPen = new Pen(Color.Blue);
int x1, x2, y1, y2;
x1 = Convert.ToInt32(i * pictureBox3.Width / gen_GA);
y1 = pictureBox3.Height - Convert.ToInt32(history_best_fit_GA[i] * pictureBox3.Height / first_fit_GA / 2);
x2 = Convert.ToInt32((i+1) * pictureBox3.Width / gen_GA);
y2 = pictureBox3.Height - Convert.ToInt32(history_best_fit_GA[i+1] * pictureBox3.Height / first_fit_GA / 2);
g.DrawLine(myPen, x1, y1, x2, y2); //这句执行第二次时，即i=1时，x1=3,x2=6,y1=103,y2=106，于是我用常数代入，一样报参数无效的错

myPen = new Pen(Color.Red);
y1 = pictureBox3.Height - Convert.ToInt32(history_avg_fit_GA[i] * pictureBox3.Height / first_fit_GA / 2);
y2 = pictureBox3.Height - Convert.ToInt32(history_avg_fit_GA[i+1] * pictureBox3.Height / first_fit_GA / 2);
g.DrawLine(myPen, x1, y1, x2, y2);

//释放绘图资源
myPen.Dispose();
g.Dispose();
}

[此贴子已经被作者于2007-11-6 9:32:24编辑过]

不是吧，我画直线啊，没画三角形，也不涉及角度。。。

都调试过了，值也看到了。。。分别是3，103，6，106，类型定死的int型，也不会出错。。。而且奇怪的是第一个i=0值运行正常，i=1时运行才出错，而两次代码又没改过。

for (int i = 0; i < gen_GA-1; i++)
{
//绘制进化曲线
Pen myPen = new Pen(Color.Blue);
int x1, x2, y1, y2;
x1 = Convert.ToInt32(i * pictureBox3.Width / gen_GA);
y1 = pictureBox3.Height - Convert.ToInt32(history_best_fit_GA[i] * pictureBox3.Height / first_fit_GA / 2);
x2 = Convert.ToInt32((i+1) * pictureBox3.Width / gen_GA);
y2 = pictureBox3.Height - Convert.ToInt32(history_best_fit_GA[i+1] * pictureBox3.Height / first_fit_GA / 2);
g.DrawLine(myPen, x1, y1, x2, y2);

myPen = new Pen(Color.Red);
y1 = pictureBox3.Height - Convert.ToInt32(history_avg_fit_GA[i] * pictureBox3.Height / first_fit_GA / 2);
y2 = pictureBox3.Height - Convert.ToInt32(history_avg_fit_GA[i+1] * pictureBox3.Height / first_fit_GA / 2);
g.DrawLine(myPen, x1, y1, x2, y2);

//释放绘图资源
myPen.Dispose();
g.Dispose(); //这句错了，应该放在循环外面。
}

问题找到了。。。用红字写出了，太粗心了，谢谢各位帮忙哦！