try
{
int a = Convert.ToInt32(Microsoft.VisualBasic.Interaction.InputBox("Enter your first number?","Title",""));
int b = Convert.ToInt32(Microsoft.VisualBasic.Interaction.InputBox("Enter your second number?","Title",""));
MessageBox.Show(a + b);
}
catch (Exception ex)
{
MessageBox.Show(ex.message);
}