var ok = new SqlConnection();
        ok.ConnectionString = @"Data Source=.\SQLEXPRESS;Integrated Security=True;User Instance=True";//连接字符串
        ok.Open();
        var cn = new SqlCommand();
        cn.Connection = ok;
        //假设你的textbox的id是companyName
        cn.CommandText = "INSERT INTO userRgs (companyName) VALUES("+companyName.Text.Trim()+")";
        cn.ExecuteNonQuery();
        ok.Close();