数学运算符不能应用于'double'和'string'类型的操作数

我在equals按钮上有错误.

private void button25_Click(object sender, EventArgs e)
{
    lblShowOp.Text = "";
    switch (operation)
    {
        case "+":
            tb1.Text = (results + Double.Parse(tb1.Text).ToString());
            break;
        case "-":
            // operator '-' cannot be applied to operands of type 'double and string'
            tb1.Text = (results - Double.Parse(tb1.Text).ToString());
            break;
        case "*":
            // operator '*' cannot be applied to operands of type 'double and string'
            tb1.Text = (results * Double.Parse(tb1.Text).ToString());
            break;
        case "/":
            // operator '/' cannot be applied to operands of type 'double and string'
            tb1.Text = (results / Double.Parse(tb1.Text).ToString());
            break;
    }
}

Charles Mage.. 8

Double.Parse(tb1.Text).ToString() 将解析为一个数字然后转换回字符串.

根据错误消息,您不能向字符串添加数字(或乘以,减去等).

你的括号在错误的地方.改变一下:

tb1.Text = (results + Double.Parse(tb1.Text).ToString());

对此:

tb1.Text = (results + Double.Parse(tb1.Text)).ToString();

并且对于其他每个人都是如此.

Double.Parse(tb1.Text).ToString() 将解析为一个数字然后转换回字符串.

根据错误消息,您不能向字符串添加数字(或乘以,减去等).

你的括号在错误的地方.改变一下:

tb1.Text = (results + Double.Parse(tb1.Text).ToString());

对此:

tb1.Text = (results + Double.Parse(tb1.Text)).ToString();

并且对于其他每个人都是如此.