C#中的数字总和

int sum = 0;
for (int i = 1; i <= 10; i++)
{
    sum += i;
}
Console.WriteLine("The sum is: " + sum);

int sum = 0;
int i = 1;
while (i <= 10)
{
    sum += i;
    i++;
}
Console.WriteLine("The sum is: " + sum);

using System.Linq;

int sum = Enumerable.Range(1, 10).Sum();
Console.WriteLine("The sum is: " + sum);