请问c#winform修改MySQL数据库时报错怎么办？

修改MySQL数据库表时报错

string M_str_sql = "server=localhost;User Id=root;password=123456;port=3306;Database=text";
MySqlConnection SQLCon = new MySqlConnection(M_str_sql);
SQLCon.ConnectionString = M_str_sql;
MySqlCommand SQLCmd;
SQLCon.Open();
try
{
string sql = "update signal1 set signal='" + "1" + "'where ip=" + "1";
SQLCmd = new MySqlCommand(sql, SQLCon);
SQLCmd.ExecuteNonQuery();
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message, "提示", MessageBoxButtons.OK);
}

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'signal = '1' where id = 1' at line 1”

我的解答思路和尝试过的方法

我想要达到的结果

string sql = "update signal1 set signal='" + "1" + "'where ip=" + "1";
这一串报错。