类方法中的随机数生成器

Question

This is part of a method inside of a class class. My goal is to generate a random number that number will be stored in a variable called iCell. After that, iCell will be used for the switch statement to change the character, cell. I am getting an error from the iCell = Random.Next(1,9); line that says "Error, An object reference is required for the non-static field, method, or property 'System.Random.Next(int, int)'". Is it not possible to have a random number generator in a class method?

 public void CPUMove() //method marks cell for CPU
    char cell;
    int iCell;
    Random rand = new Random();
    iCell = Random.Next(1, 9);
    switch (iCell)
    {
        case 1:
            cell = '1';
        break;
        case 2:
            cell = '2';
        break;
        case 3:
            cell = '3';
        break;
        case 4:
            cell = '4';
        break;
        case 5:
            cell = '5';
        break;
        case 6:
            cell = '6';
        break;
        case 7:
            cell = '7';
        break;
        case 8:
            cell = '8';
        break;
        case 9:
            cell = '9';
        break;
    }

Answer 1

iCell = rand.Next(1, 9);

Use the object you already created.

Please note that you should create this Random instance once in your program. Maybe you can make it a class variable or even a static class variable.

Answer 2

You want rand.Next rather than Random.Next so that you're referencing the instance you just created

Also, you can get rid of that big switch statement. Just write:

cell = iCell.ToString()[0];

Answer 3

In addition to other answers: better off making the Random instance static.

class MyClass {
    static Random rand = new Random();

    public void CPUMove() { //method marks cell for CPU
        char cell;
        int iCell;
        iCell = rand.Next(1, 9);
        cell = iCell.ToString()[0];
    }
}

Answer 4

You can do it like that:

// Simplest case, not thread safe
// The same generator for all CPUMove() calls
private static Random rand = new Random();

// method marks cell for CPU
public void CPUMove() {
  // Don't re-create Random each time you need a random value:
  // the values generated will be badly skewed
  // Random rand = new Random();

  // You don't need any switch/case here, just a conversion 
  Char cell = (Char) (rand.Next('1', '9')); 
  ...
}