protected void Button1_Click(object sender, EventArgs e)
{

    string text1 = TextBox3.Text;//用户名
    string text2 = TextBox4.Text;//密码
    string text3 = TextBox1.Text;//email
    string text4 = TextBox2.Text;//telphone
    SqlConnection myconn = new SqlConnection();
    string cmdtext = "insert into register values(" + "'" + text1 + "'" + "," + "'" + text2 + "'" + "," + "'" + text3 + "'"+ "," + "'" + text4 + "'"+")";
  //  string cmdtext = "select * from login where username =" + "'" + text1 + "'";
    string cmdtext0 = "select * from register where username =" + "'" + text1 + "'";

    SqlCommand mycommand = new SqlCommand(cmdtext0, myconn);
    myconn.ConnectionString = myconn_str;

    int index=0;
    // string output = "<table border=1>";
    myconn.Open();

    index = mycommand.ExecuteNonQuery();  //  ------------------>index = -1

 //   MessageBox.Show("index =" + index.ToString());

    if (index == 0) //名字没有被注册
    {
        mycommand.CommandText = cmdtext;

        index = mycommand.ExecuteNonQuery();

        if (index == 1)
        {
            MessageBox.Show("Register successfully");

        }

    }
    else if(index == 1)
    {
        MessageBox.Show("Your name is already existed!");
        empty();
    }
    else
    {
        MessageBox.Show("system exception");
    }
    myconn.Close();
 
}