FormatException未处理：输入字符串格式不正确

Question

我无法乘以两个文本框的值。

private void button1_Click(object sender, EventArgs e)
{
    if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
    {
        textBox3.Text = (Convert.ToInt32(textBox1.Text) * Convert.ToInt32(textBox2.Text)).ToString();
    }
}

private void button2_Click(object sender, EventArgs e)
{
    if (!string.IsNullOrEmpty(textBox3.Text) && !string.IsNullOrEmpty(textBox4.Text))
    {
        textBox5.Text = (Convert.ToInt32(textBox3.Text) + Convert.ToInt32(textBox4.Text)).ToString();
    }
}

Answer 1

这是指向正确方向的东西......

    private void button1_Click(object sender, EventArgs e)
    {
        float tbox1 = float.Parse(textBox1.Text);
        float tbox2 = float.Parse(textBox2.Text);
        float tbox12;

        if (textBox1 != null && textBox2 != null)
        {
            tbox12 = tbox1 + tbox2;
            textBox3.Text = tbox12.ToString();
        }
    }

    private void button2_Click(object sender, EventArgs e)    
    {
        float tbox3 = float.Parse(textBox3.Text);
        float tbox4 = float.Parse(textBox4.Text);
        float tbox34;

        if (textBox3 != null && textBox4 != null)
        {
           tbox34 =  tbox3 + tbox4;
           textBox5.Text = tbox34.ToString();
        }       

    }