引用参数，值参数，ref,out

1，一个参数只有在引用的时候才能改变其值，这是一种情况

2，一个参数在引用后要永久的改变其值（可以用返回参数的形式）

3，多个参数在引用后要永久的改变其值或者多个参数中的部分，多个参数时如果要输出一个参数的话要用OUT（输出多个的话用多个OUT），当然要注意，如果一个参数不是输出值就不能用OUT

4，OUT就是输出的意思，老外起名不会瞎起的，呵呵

有时候我们可以“顾名思义”  OK上例子

1

static void ShowDouble(int val)
{
val *= 2;
Console.WriteLine("val doubled = {0}", val);
}


int myNumber = 5;
Console.WriteLine("myNumber = {0}", myNumber);
ShowDouble(myNumber);
Console.WriteLine("myNumber = {0}", myNumber);

2

static int DoubleNum(int val)
{
val *= 2;
return val;
}




int myNumber = 5;
Console.WriteLine("myNumber = {0}", myNumber);
myNumber = DoubleNum(myNumber);
Console.WriteLine("myNumber = {0}", myNumber);

3。REF

static void ShowDouble(ref int val)
{
val *= 2;
Console.WriteLine("val doubled = {0}", val);
}


int myNumber = 5;
Console.WriteLine("myNumber = {0}", myNumber);
ShowDouble(ref myNumber);
Console.WriteLine("myNumber = {0}", myNumber);

4. OUT

static int MaxValue(int[] intArray, out int maxIndex)
{
int maxVal = intArray[0];
maxIndex = 0;
for (int i = 1; i < intArray.Length; i++)
{
if (intArray[i] > maxVal)
{
maxVal = intArray[i];
maxIndex = i;
}
}
return maxVal;
}



int[] myArray = { 1, 8, 3, 6, 2, 5, 9, 3, 0, 2 };
int maxIndex;
Console.WriteLine("The maximum value in myArray is {0}",
MaxValue(myArray, out maxIndex));
Console.WriteLine("The first occurrence of this value is at element {0}",
maxIndex + 1);