如何通过单击按钮为两个表插入数据

Question

我试图将数据插入两个表中，但只插入了第一个表中。

这是我的代码：

// on click I want to insert data into two tables
private void Button_Click(object sender, RoutedEventArgs e) 
{
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = ConfigurationManager.ConnectionStrings["MyTable"].ConnectionString;

    try
    {
        conn.Open();

        SqlCommand cmd = new SqlCommand("INSERT INTO [User] (User_Id, First_Name, LastName, BirthDay,[Group], Password, IsTeacher, Email, Gender, Extra_Time, Average) VALUES ('" + userid.Text + "','" + firstname.Text + "','" + lastname.Text + "','" + birthday.Text + "','" + gruop.Text + "','" + password.Text + "','" + teachername.Text + "','" + email.Text + "','" + gender.Text + "','" + extratime.Text + "','" + average.Text + "')", conn);//insert into first table

        SqlCommand cmd_2 = new SqlCommand("INSERT INTO [User_Login](First_Name, Last_Name, StudentOrTeacher, Password) VALUES ('" + userid.Text + "','" + firstname.Text + "','" + lastname.Text + "','Student','"+password+"',)",conn);insert into second table

        if (FillCheck() == 0)     // check if all data inserted
        {
            binddatagrid();
        }
        else
        {
            int result = (int)cmd.ExecuteScalar();
            conn.Close();

            if (result > 0)
            {
                MessageBox.Show("Successful Login");
            }
            else
            {
                MessageBox.Show("Incorrect Login");
            }
        }
    }
    catch (Exception ex)
    {
       Console.WriteLine(ex.Message);   //Error message
    }
    finally
    {
        Console.ReadLine();
    }
}

我得到一个错误：

  

对象引用未设置为对象实例