输入字符串的格式不正确

Question

下面的代码会产生错误，说明我的输入字符串格式不正确。为什么呢？

private void button7_Click(object sender, EventArgs e)
{
    string uriAddTagtoGroup = 
      string.Format("http://localhost:8000/Service/AddTagtoGroup/{group}/{tag}",
                    textBox6.Text, textBox7.Text);
    //line above says input string was not in the correct format?
}

Answer 1

 string.Format("http://localhost:8000/Service/AddTagtoGroup/{0}/{1}", 
                textBox6.Text, textBox7.Text);

使用序数