c# - 矩形没有通过 SQLDataReader while 子句绘制

Question

为什么矩形没有绘制？我的代码有什么错误吗？我尝试通过 SQLDataReader while 子句创建一个矩形..

private void PrintsDoc (object sender, PrintPageEventArgs e)
{
    Graphics g = e.Graphics;
    StringFormat sf = new StringFormat ();
    sf.Alignment = StringAlignment.Center;
    sf.LineAlignment = StringAlignment.Near;

    Font fontStyle = new Font ("Times New Roman", 30);
    Font fontStyle2 = new Font ("Times New Roman", 10);
    g.DrawString ("Trade Confirmation", fontStyle, Brushes.Black, e.MarginBounds, sf);
    g.DrawString ("\n\n\nTrade Date: " + dt + "\nPrint Date: " + DateTime.Now.ToString (), fontStyle2, Brushes.Black, e.MarginBounds, sf);

    SqlConnection conn = new SqlConnection("Server=WORKERCOMP\\SQLEXPRESS;" + "Database=database;" + "User ID=uid;" + "Password=pwd;" + "Trusted_Connection=yes;");
    conn.Open ();

    int i = 0, j = 0;
    SqlCommand cmd = new SqlCommand("SELECT COLUMN_NAME, DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'dbo.TRADE'", conn);
    SqlDataReader rdr = cmd.ExecuteReader ();
    while (rdr.Read ()) {
        Rectangle rec = new Rectangle (new Point (40 + i, 250), new Size (200, 25));
        g.DrawRectangle (Pens.Black, rec);
        g.DrawString (rdr.GetString(0 + j), fontStyle2, Brushes.Black, rec, sf);
        i = i + 215;
        j = j + 1;
    }

    e.HasMorePages = false;
    conn.Close ();
}

Answer 1

private void PrintsDoc (object sender, PrintPageEventArgs e)
{
    Graphics g = e.Graphics;
    StringFormat sf = new StringFormat ();
    sf.Alignment = StringAlignment.Center;
    sf.LineAlignment = StringAlignment.Near;

    Font fontStyle = new Font ("Times New Roman", 30);
    Font fontStyle2 = new Font ("Times New Roman", 10);
    g.DrawString ("Trade Confirmation", fontStyle, Brushes.Black, e.MarginBounds, sf);
    g.DrawString ("\n\n\nTrade Date: " + dt + "\nPrint Date: " + DateTime.Now.ToString (), fontStyle2, Brushes.Black, e.MarginBounds, sf);

    using (SqlConnection conn = new SqlConnection(@"Server=.\SQLEXPRESS;Database=database;Trusted_Connection=yes;"))
    using (SqlCommand cmd = new SqlCommand("SELECT COLUMN_NAME, DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'TRADE'", conn))
    {
    conn.Open ();
    int i = 0, j = 0;
    SqlDataReader rdr = cmd.ExecuteReader ();
    while (rdr.Read ()) {
        Rectangle rec = new Rectangle (new Point (40 + i, 250), new Size (200, 25));
        g.DrawRectangle (Pens.Black, rec);
        //g.DrawString (rdr.GetString(0 + j), fontStyle2, Brushes.Black, rec, sf);
        g.DrawString ((string)rdr["COLUMN_NAME"], fontStyle2, Brushes.Black, rec, sf);
        i = i + 215;
        j = j + 1; // what is the purpose of j?
    }

    e.HasMorePages = false;
    conn.Close ();
    }
}