NullReferenceException是一个未处理的错误,带有列表和随机
本文关键字:错误 列表 随机 未处理 一个 NullReferenceException | 更新日期: 2023-09-27 17:57:46
我有以下代码示例:
public int intTest { get; set; }
public List<int> listTest { get; set; }
//Method for creating a random number to return.
public int methodRandom()
{
Random random1 = new Random();
int intValue;
intValue = random1.Next(1, intTest + 1);
return (intValue);
}
private void button1_Click(object sender, EventArgs e)
{
intTest = int.Parse(textBox1.Text); // Will be a value between 1 and 9 in my code)
for (int i = 0; i < intTest; i++)
{
int temp = methodRandom();
listTest.Add(temp);
}
}
但当我调试并单击按钮时,我会收到以下错误消息,标记为"listTest.Add(temp);",上面写着"NullReferenceException未处理"。我做错了什么?
在向列表添加项之前,必须先实例化列表。构造函数是一个很好的位置。
public YourClass() // I don't know what the name of your class is.
{
listTest = new List<int>();
}
每次button1_Click
事件触发时,您可能需要清除该列表(除非您只是想继续向列表中添加数字)。
private void button1_Click(object sender, EventArgs e)
{
listTest.Clear(); // Clear previous items before adding new ones
...
}
private void button1_Click(object sender, EventArgs e)
{
listTest=new List<int>();
intTest = int.Parse(textBox1.Text); // Will be a value between 1 and 9 in my code)
for (int i = 0; i < intTest; i++)
{
int temp = methodRandom();
listTest.Add(temp);
}
}