问题描述
可能的重复:
随机数生成器只生成一个随机数
初学者问题.我有一个非常简单的画线程序，我想随机化位置，但是每次我创建一个新的 Random 实例时，它都会返回相同的值.哪里有问题?谢谢.
A beginner question. I have a very simple program that draws a line and I want to randomize the locations, but each time I create a new instance of Random it returns the same value. Where is the problem? Thank you.
private void Draw()
{
Random random1 = new Random();
int randomNumber1 = random1.Next(0, 300);
Random random2 = new Random();
int randomNumber2 = random2.Next(0, 300);
Random random3 = new Random();
int randomNumber3 = random3.Next(0, 300);
Random random4 = new Random();
int randomNumber4 = random4.Next(0, 300);
System.Drawing.Graphics g = this.CreateGraphics();
Pen green = new Pen(Color.Green, 5);
g.DrawLine(green, new Point(randomNumber1, randomNumber2),
new Point(randomNumber3, randomNumber4));
}
private void btndraw1_Click(object sender, EventArgs e)
{
Draw();
}
推荐答案
发生这种情况的原因是每次你做一个新的 Random 时，它都会使用时钟进行初始化.所以在一个紧密的循环中(或者一个接一个的多次调用)你会多次得到相同的值，因为所有这些随机变量都是用相同的种子初始化的.
The reason this happens is that every time you do a new Random it is initialized using the clock. So in a tight loop (or many calls one after the other) you get the same value lots of times since all those random variables are initialized with the same seed.
要解决这个问题:只创建一个随机变量，最好在你的函数之外，并且只使用那个实例.
To solve this: Create only one Random variable, preferably outside your function and use only that one instance.
Random random1 = new Random();
private void Draw()
{
int randomNumber1 = random1.Next(0, 300);
int randomNumber2 = random1.Next(0, 300);
int randomNumber3 = random1.Next(0, 300);
int randomNumber4 = random1.Next(0, 300);
System.Drawing.Graphics g = this.CreateGraphics();
Pen green = new Pen(Color.Green, 5);
g.DrawLine(green, new Point(randomNumber1, randomNumber2), new Point(randomNumber3, randomNumber4));
}
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