我对 INSTERT 语句有问题。 我从网格viev 获得数据, 效果很好, 但我不能把它们插入表格

private void button3_Click(object sender, EventArgs e)
{
    int amorplanid = 0;
    int idn = 0;
    DateTime datum;
    double interest = 0;
    double principal = 0;
    double payment = 0;
    double newprincipal = 0;

    string nizz = "";
    string[] niz= new string[7];
    for (int x = 0; x < dataGridView1.Rows.Count-1; x++)
    {
        for (int j = 0; j < dataGridView1.Rows[x].Cells.Count; j++)
        {
            nizz += dataGridView1.Rows[x].Cells[j].Value.ToString()+"."; 
        }
        niz = nizz.Split( . );

        amorplanid = System.Convert.ToInt32(niz[0]);
        idn = System.Convert.ToInt32(niz[1]);
        // datum = System.Convert.ToDateTime(niz[2]);
        datum = DateTime.Now;
        interest = System.Convert.ToDouble(niz[3]);
        principal = System.Convert.ToDouble(niz[4]);
        payment = System.Convert.ToDouble(niz[5]);
        newprincipal = System.Convert.ToDouble(niz[6]);

        String insert = @"INSERT INTO AmortPlanCoupT(ID, AmortPlanID, CoupDate, Interest, Principal, Payxment, NewPrincipal) VALUES (" + idn + "," + amorplanid + "," + datum + "," + (float)interest + "," + (float)principal + "," + (float)payment + "," + (float)newprincipal + ")";
        SqlConnection myconn = new SqlConnection(conn);
        // String MyString = @"INSERT INTO Employee(ID, FirstName, LastName) VALUES(2,  G ,  M )";
        try
        {
            myconn.Open();
            SqlCommand cmd = new SqlCommand(insert, myconn);
            cmd.ExecuteNonQuery();
            myconn.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }
    }

    label14.Text = niz[0];
}

我创建了一个 Windows 控制台应用程序来测试 :

我有表 test , 有两个列 id(int), leto(float) ;

SqlConnection MyConnection = new SqlConnection(@"Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|App_DataDatabase1.mdf;Integrated Security=True;User Instance=True");

try
{
    MyConnection.Open();

    String MyString = @"INSERT INTO test(id, leto) VALUES(2, 2)";
    SqlCommand MyCmd = new SqlCommand(MyString, MyConnection);

    MyCmd.ExecuteScalar();
    MyConnection.Close();
}
catch (Exception e)
{
    Console.WriteLine(e.ToString());
}

我一直在尝试不同的东西 写数据到桌子上, 只是不能让他们在那里。