表单，文本框 + 文本框 = 文本框，输入两个整数，求和

private void button1_Click_1(object sender, EventArgs e)

{

string number1 = textBox1.Text;

string number2 = textBox2.Text;

int numberInt1, numberInt2, numberInt3;

if (!int.TryParse(number1, out numberInt1))

{

MessageBox.Show("请输入整数！");

return;

}

if (!int.TryParse(number2, out numberInt2))

{

MessageBox.Show("请输入整数！");

return;

}

numberInt3 = numberInt1 + numberInt2;

string number3 = numberInt3.ToString();

textBox3.Text = number3;

}