c# - printdocument 添加空白页

Question

我正在尝试使用 printdocument 从数据库中打印数据，我将其打印到指定范围内的数据，但仍有两处出错

仍然没有按预期工作的事情是

• 在打印时，如果页面几乎被完全使用，它会添加一个空白页面，上面只打印一个标题
• 如果一页已满，则下一页再次从该范围的第一项开始(通过使用多个列表修复，因为我无法弄清楚如何使用子列表制作列表)

这是我必须调用打印文档的代码

private void button3_Click(object sender, EventArgs e)//print
{
    range();
    try
    {
        if (artikel == true)
        {
            itemperpage = totalnumber = 0;
            printPreviewDialog1.Document = printDocument1;
            print = true;
            printDocument1.Print();
            // this.Close();
        }
    }
    catch (Exception q) { MessageBox.Show("" + q); }
}

这是打印文档的代码

private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
{
    if (artikel == true)
    {
        Font messageFont = new Font("Arial", 14, System.Drawing.GraphicsUnit.Point);

        float currentY = 10;// declare  one variable for height measurement 
        e.Graphics.DrawString("                                                                                                                  I N K O O P A R T I K E L E N ", DefaultFont, Brushes.Black, 10, currentY);//this will print one heading/title in every page of the document 
        currentY += 15;

        SqlCommand artprint = new SqlCommand("select * from ART WHERE ART BETWEEN @range AND @range2 ORDER BY ART ASC", Connectie.connMEVO_ART);
        if (comboBox1.SelectedIndex <= comboBox2.SelectedIndex)
        {
            artprint.Parameters.Add("@range", SqlDbType.VarChar).Value = comboBox1.SelectedItem;
            artprint.Parameters.Add("@range2", SqlDbType.VarChar).Value = comboBox2.SelectedItem;
        }
        else if (comboBox2.SelectedIndex <= comboBox1.SelectedIndex)
        {
            artprint.Parameters.Add("@range", SqlDbType.VarChar).Value = comboBox2.SelectedItem;
            artprint.Parameters.Add("@range2", SqlDbType.VarChar).Value = comboBox1.SelectedItem;
        }
        drART = artprint.ExecuteReader();
        try
        {
            while (totalnumber <= amount - 1 && drART.Read())
            {// check the number of items 
                tostring();//SQL data to string
                row = row + Environment.NewLine + "ART            LEV         LTD       MVRD   SGR        INK        CRNI    " + " VALUTA    KOR ";
                row = row + Environment.NewLine + aa + "  " + a + "  " + b + "  " + c + "  " + d + "  " + m + "  " + f + "   " + g + "          " + h;
                row = row + Environment.NewLine + "EH2     EH1      EF            OMS     ";
                row = row + Environment.NewLine + j + "         " + k + "         " + l + "  " + i;
                row = row + Environment.NewLine;
                e.Graphics.DrawString(row, DefaultFont, Brushes.Black, 50, currentY);//print each item
                Debug.WriteLine("" + row);
                row = "";
                currentY += 80; // set a gap between every item
                totalnumber += 1; //increment count by 1
                if (itemperpage <= 12) 
                {
                    itemperpage += 1; // increment itemperpage by 1
                    e.HasMorePages = false; // set the HasMorePages property to false , so that no other page will not be added 
                }
                else // if the number of item(per page) is more than 12 then add one page 
                {
                    itemperpage = 0; //initiate itemperpage to 0 .  
                    e.HasMorePages = true; //e.HasMorePages raised the PrintPage event once per page .           
                    return;//It will call PrintPage event again   
                }
            }
        }
        catch (Exception ef)
        {
            MessageBox.Show("" + ef);
        }
        artprint.Dispose();
    }
}

private void tostring()
{
    aa = drART["ART"].ToString();
    for (int ss = aa.Length; ss < 8; ss++) { aa = aa + " "; }
    a = drART["LEV"].ToString();
    for (int ss = a.Length; ss < 10; ss++) { a = a + " "; }
    b = drART["LTD"].ToString();
    for (int ss = b.Length; ss < 10; ss++) { b = b + " "; }
    c = drART["MVRD"].ToString();
    for (int ss = c.Length; ss < 10; ss++) { c = c + " "; }
    d = drART["SGR"].ToString();
    for (int ss = d.Length; ss < 10; ss++) { d = d + " "; }
    m = drART["INK"].ToString();
    for (int ss = m.Length; ss < 10; ss++) { m = m + " "; }
    f = drART["CRNI"].ToString();
    for (int ss = f.Length; ss < 10; ss++) { f = f + " "; }
    g = drART["VALUTA"].ToString();
    for (int ss = g.Length; ss < 3; ss++) { g = g + " "; }
    h = drART["KOR"].ToString();
    for (int ss = h.Length; ss < 10; ss++) { h = h + " "; }
    i = drART["OMS"].ToString();
    j = drART["EH2"].ToString();
    for (int ss = j.Length; ss < 3; ss++) { j = j + " "; }
    k = drART["EH1"].ToString();
    for (int ss = k.Length; ss < 3; ss++) { k = k + " "; }
    l = drART["EF"].ToString();
    for (int ss = l.Length; ss < 10; ss++) { l = l + " "; }
}

Answer 1

您写道您使用了来自网络的资源，我想这表明了这一点。我们都这样做，但对它们的质量持怀疑态度真的很重要。当然，结合两个来源很可能根本行不通。

我将首先讨论您的代码的几个问题，然后向您展示如何在多个页面上打印 DB 中的项目的示例。

请帮自己一个忙，小心选择变量的名称!是的，这需要更长的时间，但它会付出代价，相信我。 (如果你不能想出任何令人信服的东西，退后一步!这通常表明你对问题的理解不够透彻......)

我们来看一些:有currentY，挺好的。而且还有itemperpage，totalnumber和amount，这都太可怕了!他们要么完全不清楚，要么甚至具有误导性!

让我们设置一些更好的名字:

// layout variables
int itemsPerPage = 40;  // how many items fit on one page
int itemHeight = 25;    // height of one item in the chosen unit

// print job variables
int totalNumber = -1;   // total number of records/items coming from the dbms
int itemsToPrint = 75;  // total number of items we want to print

// print progress variables
int itemsPrinted = 0;   // number of items printed so far
int pagesPrinted = 0;   // number of pages printed

另一个问题是你选择的单位，或者准确地说是没有选择单位。默认 GraphicsUnit是 Display 打印总计 1/100 英寸。如果你喜欢，我建议用代码编写它来记录它。这个单元将在整个布局过程中使用，所以它应该在代码中可见!我个人更喜欢毫米。还有其他几个单位..选择你的但记录下来!

您应该查看的另一件事是 String.Format()和 string.PadLeft() .它们比 tostring() 方法中的循环要好得多!

现在让我们看看您的具体问题:

一旦我们使用了足够多的变量，这些变量的名称无需学习就可以真正理解。

另一个问题是您设置 DB 读取的方式:您需要在开始打印的位置而不是在 PrintPage 循环中设置读取器。注意:这些实际上是两个循环:一个是可见的while (...reader.Read() )，另一个是隐式:整个 PrintPage 事件本身就是循环体。

首先让我们看一下range() 代码。我已经把它变成了一个返回最大记录数的函数。我第一步获取计数。然后我为真正的读取设置了 DataReader，这将在 PrintPage 事件中发生:我枚举字段以便我可以控制它们的顺序并且不拉入我不需要的东西。

请注意，我使用的是 MySql，但类几乎相同，只是带有 MySQl 前缀。我不在此处包括连接代码。当然，我是从我自己的数据库中读取的……

MySqlConnection DBC = new MySqlConnection("");
MySqlCommand CMD = null;
MySqlDataReader DR = null;

int range ()
{
    CMD = new MySqlCommand("select count(0) from test.artists ", DBC);
    var count = CMD.ExecuteScalar();
    int counter = Convert.ToInt32(count);
    CMD = new MySqlCommand("select artist_ID, artist, genres from test.artists ", DBC);
    DR = CMD.ExecuteReader();
    return (int)counter;
}

现在让我们看看打印命令，使用上面的变量:

private void cb_print_Click(object sender, EventArgs e)
{
    totalNumber = range();
    try
    {
        if (DBC.State == ConnectionState.Open)
        {
            pagesPrinted = 0;
            printPreviewDlg.Document = printDocument1;
            printPreviewDlg.ShowDialog();
        }
    } catch (Exception q) { MessageBox.Show("" + q); }
    DR.Dispose();
}

请注意，Reader 是在 range 调用中创建的!

最后是 PrintPage 事件:

private void printDocument1_PrintPage(object sender, 
                            System.Drawing.Printing.PrintPageEventArgs e)
{
    // my page unit
    e.Graphics.PageUnit = GraphicsUnit.Millimeter;

    // starting a new page
    int itemsOnPage = 0;
    pagesPrinted++;

    float currentY = 12;
    e.Graphics.DrawString(String.Format(
               "HEADER -  printing {0} items of {1}    - Page {2}",
               itemsToPrint, totalNumber, pagesPrinted), 
               Font, Brushes.Black, 1, currentY);  

    currentY += 30;  // header height

    try
    {
        // page is not full and we want to print more items
        while (itemsOnPage < itemsPerPage && itemsPrinted < itemsToPrint - 1
               && DR.Read())
        {
            string row = String.Format("{0,5:000} Artist: {1,20}  ({2})   ",
                                         DR[0], DR[1], DR[2]);

            e.Graphics.DrawString(row, DefaultFont, Brushes.Black, 50, currentY);  
            // Console.WriteLine("" + row);

            currentY += itemHeight; 
            itemsPrinted++; 
            itemsOnPage++;

            // we want to print more items but now the page is full
            if ( itemsPrinted < itemsToPrint && itemsOnPage >= itemsPerPage)
            {
                itemsOnPage = 0;        
                e.HasMorePages = true;         
                return;                 
            }
            else 
            {
                // this will only be used after all data are printed
                e.HasMorePages = false; 
            }
        }
    } catch (Exception ef)
    {
        MessageBox.Show("" + ef);
    }
}