using System.Windows.Forms;
int sum=0;
for (int i=0;i < 10;i++)
{
sum += i;
}
MessageBox.Show(sum.ToString()); //45
MessageBox.Show(sum.ToString(),"The sum is:");
MessageBox.Show(sum.ToString(), "The sum is:",MessageBoxButtons.YesNo);
DialogResult dr = MessageBox.Show(sum.ToString(), "The sum is:",MessageBoxButtons.YesNo);
if (dr == DialogResult.Yes) {...}
else if (dr == DialogResult.No) {...}