从多列listview c打印数据

Question

我查看多列列表框中收到的所有数据。当我点击打印按钮时，它将打印出列表框中的所有数据查看。

这是我的代码：

1。首先，用户将根据ID搜索关键字。然后它将出现在多列listview中。这个数据是在xml文件中搜索。

XmlDocument xml = new XmlDocument();
xml.Load("C:\\Users\\HDAdmin\\Documents\\Fatty\\SliceEngine\\SliceEngine\\bin\\Debug\\patient.xml");
XmlNodeList xnList = xml.SelectNodes("/main/patient");
foreach (XmlNode xn in xnList)
{
    string date = xn.OfType<XmlNode>().FirstOrDefault(n => n.Name == "Date").FirstChild.Value;
    string id = xn.OfType<XmlNode>().FirstOrDefault(n => n.Name == "ID").FirstChild.Value;
    if (date == cari)
    {
       listviewitem = new ListViewItem(date);
       listviewitem.SubItems.Add("Smith");
       this.listView1.Items.Add(listviewitem);
    }
       if (id == cari)
       {                    
           listviewitem = new ListViewItem(date);

           id = xn.OfType<XmlNode>().FirstOrDefault(n => n.Name == "ID").FirstChild.Value;
           listviewitem.SubItems.Add(id);

           string level = xn.OfType<XmlNode>().FirstOrDefault(n => n.Name == "Level").FirstChild.Value;
           listviewitem.SubItems.Add(level);

           string name = xn.OfType<XmlNode>().FirstOrDefault(n => n.Name == "Name").FirstChild.Value;                    
           listviewitem.SubItems.Add(name);

2。在同一方法中，我添加了打印事件按钮

    this.components = new System.ComponentModel.Container();
    this.printBut = new System.Windows.Forms.Button();
    this.ClientSize = new System.Drawing.Size(504, 381);
    this.Text = "Print Example";

    printBut.ImageAlign = System.Drawing.ContentAlignment.MiddleLeft;               
    printBut.Location = new System.Drawing.Point(32, 110);
    printBut.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
    printBut.TabIndex = 0;
    printBut.Text = "Print the file.";
    printBut.Size = new System.Drawing.Size(136, 40);
    printBut.Click += new System.EventHandler(printBut_Click);

    this.Controls.Add(printBut);
    //-------------print-----------------

3。这是printBut_click。

private void printBut_Click(object sender, EventArgs e)
    {
        try
        {
            StreamReader streamToPrint = new StreamReader("C:\\Users\\HDAdmin\\Documents\\Fatty\\SliceEngine\\SliceEngine\\bin\\Debug\\aboutREPCS.txt");

            try
            {
                printFont = new Font("Arial", 10);
                pd = new PrintDocument();
                pd.PrintPage += new PrintPageEventHandler(this.pd_PrintPage);                       
                pd.Print();
            }
            finally
            {
                streamToPrint.Close();
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

4. 这是printPage事件

// The PrintPage event is raised for each page to be printed.
private void pd_PrintPage(object sender, PrintPageEventArgs ev)
    {
        float linesPerPage = 0;
        float yPos = 0;
        int count = 0;
        float leftMargin = ev.MarginBounds.Left;
        float topMargin = ev.MarginBounds.Top;
        string line = null;

        // Calculate the number of lines per page.
        linesPerPage = ev.MarginBounds.Height /
           printFont.GetHeight(ev.Graphics);

        // Print each line of the file.
        while (count < linesPerPage &&
           ((line = streamToPrint.ReadLine()) != null))
        {
            yPos = topMargin + (count *
               printFont.GetHeight(ev.Graphics));
            ev.Graphics.DrawString(line, printFont, Brushes.Black,
               leftMargin, yPos, new StringFormat());
            count++;
        }

        // If more lines exist, print another page.
        if (line != null)
            ev.HasMorePages = true;
        else
            ev.HasMorePages = false;
    }

当我运行此代码时，它显示为object reference not set to an instance of an object。

所以，让我重复一下这个应用程序的流程。

User insert keyword.
If keyword match, view data from xml file into multicolumn listview.
printBut will print all the data view in listview.