Guide pratique pour imprimer dans Windows Forms à l’aide de l’aperçu avant impression

Il est très courant dans la programmation Windows Forms d’offrir un aperçu avant impression en plus des services d’impression. Un moyen simple d’ajouter des services d’aperçu avant impression à votre application consiste à utiliser un contrôle PrintPreviewDialog en combinaison avec la logique de gestion des événements PrintPage pour l’impression d’un fichier.

Pour afficher un aperçu d’un document texte avec un contrôle PrintPreviewDialog

1. Ajoutez un PrintPreviewDialog, un PrintDocumentet deux chaînes à votre formulaire.

   private PrintPreviewDialog printPreviewDialog1 = new PrintPreviewDialog();
   private PrintDocument printDocument1 = new PrintDocument();
   
   // Declare a string to hold the entire document contents.
   private string documentContents;
   
   // Declare a variable to hold the portion of the document that
   // is not printed.
   private string stringToPrint;
   

   Private printPreviewDialog1 As New PrintPreviewDialog()
   Private WithEvents printDocument1 As New PrintDocument()
   
   ' Declare a string to hold the entire document contents.
   Private documentContents As String
   
   ' Declare a variable to hold the portion of the document that
   ' is not printed.
   Private stringToPrint As String
   

2. Définissez la propriété DocumentName sur le document que vous souhaitez imprimer, puis ouvrez et lisez le contenu du document sur la chaîne que vous avez ajoutée précédemment.

   private void ReadDocument()
   {
       string docName = "testPage.txt";
       string docPath = @"c:\";
       printDocument1.DocumentName = docName;
       using (FileStream stream = new FileStream(docPath + docName, FileMode.Open))
       using (StreamReader reader = new StreamReader(stream))
       {
           documentContents = reader.ReadToEnd();
       }
       stringToPrint = documentContents;
   }
   

   Private Sub ReadDocument() 
       Dim docName As String = "testPage.txt"
       Dim docPath As String = "c:\"
       printDocument1.DocumentName = docName
       Dim stream As New FileStream(docPath + docName, FileMode.Open)
       Try
           Dim reader As New StreamReader(stream)
           Try
               documentContents = reader.ReadToEnd()
           Finally
               reader.Dispose()
           End Try
       Finally
           stream.Dispose()
       End Try
       stringToPrint = documentContents
   
   End Sub
   

3. Comme vous le feriez pour imprimer le document, dans le gestionnaire d’événements PrintPage, utilisez la propriété Graphics de la classe PrintPageEventArgs et le contenu du fichier pour calculer les lignes par page et afficher le contenu du document. Une fois chaque page dessinée, vérifiez s’il s’agit de la dernière page et définissez la propriété HasMorePages du PrintPageEventArgs en conséquence. L’événement PrintPage est déclenché jusqu’à ce que HasMorePages soit false. Une fois le rendu terminé, réinitialisez la chaîne à rendre. Vérifiez également que l’événement PrintPage est associé à sa méthode de gestion des événements.

   Note

   Vous avez peut-être déjà effectué les étapes 2 et 3 si vous avez implémenté l’impression dans votre application.

   Dans l’exemple de code suivant, le gestionnaire d’événements est utilisé pour imprimer le fichier «testPage.txt» dans la même police utilisée sur le formulaire.

   void printDocument1_PrintPage(object sender, PrintPageEventArgs e)
   {
       int charactersOnPage = 0;
       int linesPerPage = 0;
   
       // Sets the value of charactersOnPage to the number of characters
       // of stringToPrint that will fit within the bounds of the page.
       e.Graphics.MeasureString(stringToPrint, this.Font,
           e.MarginBounds.Size, StringFormat.GenericTypographic,
           out charactersOnPage, out linesPerPage);
   
       // Draws the string within the bounds of the page.
       e.Graphics.DrawString(stringToPrint, this.Font, Brushes.Black,
       e.MarginBounds, StringFormat.GenericTypographic);
   
       // Remove the portion of the string that has been printed.
       stringToPrint = stringToPrint.Substring(charactersOnPage);
   
       // Check to see if more pages are to be printed.
       e.HasMorePages = (stringToPrint.Length > 0);
   
       // If there are no more pages, reset the string to be printed.
       if (!e.HasMorePages)
           stringToPrint = documentContents;
   }
   

   Sub printDocument1_PrintPage(ByVal sender As Object, _
       ByVal e As PrintPageEventArgs) Handles printDocument1.PrintPage
   
       Dim charactersOnPage As Integer = 0
       Dim linesPerPage As Integer = 0
   
       ' Sets the value of charactersOnPage to the number of characters 
       ' of stringToPrint that will fit within the bounds of the page.
       e.Graphics.MeasureString(stringToPrint, Me.Font, e.MarginBounds.Size, _
           StringFormat.GenericTypographic, charactersOnPage, linesPerPage)
   
       ' Draws the string within the bounds of the page.
       e.Graphics.DrawString(stringToPrint, Me.Font, Brushes.Black, _
           e.MarginBounds, StringFormat.GenericTypographic)
   
       ' Remove the portion of the string that has been printed.
       stringToPrint = stringToPrint.Substring(charactersOnPage)
   
       ' Check to see if more pages are to be printed.
       e.HasMorePages = stringToPrint.Length > 0
   
       ' If there are no more pages, reset the string to be printed.
       If Not e.HasMorePages Then
           stringToPrint = documentContents
       End If
   
   End Sub
   

4. Définissez la propriété Document du contrôle PrintPreviewDialog sur le composant PrintDocument du formulaire.

   printPreviewDialog1.Document = printDocument1;
   

   printPreviewDialog1.Document = printDocument1
   

5. Appelez la méthode ShowDialog sur le contrôle PrintPreviewDialog. En général, vous appelez ShowDialog à partir de la méthode de gestion des événements Click d’un bouton. L’appel ShowDialog déclenche l’événement PrintPage et rend le résultat dans le composant PrintPreviewDialog. Lorsque l’utilisateur clique sur l’icône d’impression dans la boîte de dialogue, l’événement PrintPage est à nouveau déclenché, en envoyant la sortie à l’imprimante au lieu de la boîte de dialogue d’aperçu. C’est pourquoi la chaîne est réinitialisée à la fin du processus de rendu à l’étape 3.

   L’exemple de code suivant montre la méthode de gestion des événements Click pour un bouton sur le formulaire. Cette méthode de gestion des événements appelle les méthodes pour lire le document et afficher la boîte de dialogue Aperçu avant impression.

   private void printPreviewButton_Click(object sender, EventArgs e)
   {
       ReadDocument();
       printPreviewDialog1.Document = printDocument1;
   printPreviewDialog1.ShowDialog();
   }
   

   Private Sub printPreviewButton_Click(ByVal sender As Object, _
       ByVal e As EventArgs) Handles printPreviewButton.Click
   
       ReadDocument()
       printPreviewDialog1.Document = printDocument1
       printPreviewDialog1.ShowDialog()
   End Sub
   

Exemple

using System;
using System.Drawing;
using System.IO;
using System.Drawing.Printing;
using System.Windows.Forms;

namespace PrintPreviewApp
{
    public partial class Form1 : Form
    {
        private Button printPreviewButton;

        private PrintPreviewDialog printPreviewDialog1 = new PrintPreviewDialog();
        private PrintDocument printDocument1 = new PrintDocument();

        // Declare a string to hold the entire document contents.
        private string documentContents;

        // Declare a variable to hold the portion of the document that
        // is not printed.
        private string stringToPrint;

        public Form1()
        {
            this.printPreviewButton = new System.Windows.Forms.Button();
            this.printPreviewButton.Location = new System.Drawing.Point(12, 12);
            this.printPreviewButton.Size = new System.Drawing.Size(125, 23);
            this.printPreviewButton.Text = "Print Preview";
            this.printPreviewButton.Click += new System.EventHandler(this.printPreviewButton_Click);
            this.ClientSize = new System.Drawing.Size(292, 266);
            this.Controls.Add(this.printPreviewButton);
            printDocument1.PrintPage +=
                new PrintPageEventHandler(printDocument1_PrintPage);
        }
        private void ReadDocument()
        {
            string docName = "testPage.txt";
            string docPath = @"c:\";
            printDocument1.DocumentName = docName;
            using (FileStream stream = new FileStream(docPath + docName, FileMode.Open))
            using (StreamReader reader = new StreamReader(stream))
            {
                documentContents = reader.ReadToEnd();
            }
            stringToPrint = documentContents;
        }

        void printDocument1_PrintPage(object sender, PrintPageEventArgs e)
        {
            int charactersOnPage = 0;
            int linesPerPage = 0;

            // Sets the value of charactersOnPage to the number of characters
            // of stringToPrint that will fit within the bounds of the page.
            e.Graphics.MeasureString(stringToPrint, this.Font,
                e.MarginBounds.Size, StringFormat.GenericTypographic,
                out charactersOnPage, out linesPerPage);

            // Draws the string within the bounds of the page.
            e.Graphics.DrawString(stringToPrint, this.Font, Brushes.Black,
            e.MarginBounds, StringFormat.GenericTypographic);

            // Remove the portion of the string that has been printed.
            stringToPrint = stringToPrint.Substring(charactersOnPage);

            // Check to see if more pages are to be printed.
            e.HasMorePages = (stringToPrint.Length > 0);

            // If there are no more pages, reset the string to be printed.
            if (!e.HasMorePages)
                stringToPrint = documentContents;
        }
        private void printPreviewButton_Click(object sender, EventArgs e)
        {
            ReadDocument();
            printPreviewDialog1.Document = printDocument1;
        printPreviewDialog1.ShowDialog();
        }

        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

Imports System.Drawing
Imports System.IO
Imports System.Drawing.Printing
Imports System.Windows.Forms



Class Form1
    Inherits Form

    Private WithEvents printPreviewButton As Button
    
    Private printPreviewDialog1 As New PrintPreviewDialog()
    Private WithEvents printDocument1 As New PrintDocument()
    
    ' Declare a string to hold the entire document contents.
    Private documentContents As String
    
    ' Declare a variable to hold the portion of the document that
    ' is not printed.
    Private stringToPrint As String

    Public Sub New() 
        Me.printPreviewButton = New System.Windows.Forms.Button()
        Me.printPreviewButton.Location = New System.Drawing.Point(12, 12)
        Me.printPreviewButton.Size = New System.Drawing.Size(125, 23)
        Me.printPreviewButton.Text = "Print Preview"
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.Add(Me.printPreviewButton)

    End Sub
    
    Private Sub ReadDocument() 
        Dim docName As String = "testPage.txt"
        Dim docPath As String = "c:\"
        printDocument1.DocumentName = docName
        Dim stream As New FileStream(docPath + docName, FileMode.Open)
        Try
            Dim reader As New StreamReader(stream)
            Try
                documentContents = reader.ReadToEnd()
            Finally
                reader.Dispose()
            End Try
        Finally
            stream.Dispose()
        End Try
        stringToPrint = documentContents
    
    End Sub

    Sub printDocument1_PrintPage(ByVal sender As Object, _
        ByVal e As PrintPageEventArgs) Handles printDocument1.PrintPage

        Dim charactersOnPage As Integer = 0
        Dim linesPerPage As Integer = 0

        ' Sets the value of charactersOnPage to the number of characters 
        ' of stringToPrint that will fit within the bounds of the page.
        e.Graphics.MeasureString(stringToPrint, Me.Font, e.MarginBounds.Size, _
            StringFormat.GenericTypographic, charactersOnPage, linesPerPage)

        ' Draws the string within the bounds of the page.
        e.Graphics.DrawString(stringToPrint, Me.Font, Brushes.Black, _
            e.MarginBounds, StringFormat.GenericTypographic)

        ' Remove the portion of the string that has been printed.
        stringToPrint = stringToPrint.Substring(charactersOnPage)

        ' Check to see if more pages are to be printed.
        e.HasMorePages = stringToPrint.Length > 0

        ' If there are no more pages, reset the string to be printed.
        If Not e.HasMorePages Then
            stringToPrint = documentContents
        End If

    End Sub

    Private Sub printPreviewButton_Click(ByVal sender As Object, _
        ByVal e As EventArgs) Handles printPreviewButton.Click

        ReadDocument()
        printPreviewDialog1.Document = printDocument1
        printPreviewDialog1.ShowDialog()
    End Sub

    <STAThread()>  _
    Shared Sub Main() 
        Application.EnableVisualStyles()
        Application.SetCompatibleTextRenderingDefault(False)
        Application.Run(New Form1())
    
    End Sub
End Class 

Compilation du code

Cet exemple nécessite :

• Références aux assemblys System, System.Windows.Forms, System.Drawing.

Voir aussi

• Comment : imprimer un fichier texte à plusieurs pages dans windows Forms
• Prise en charge de l’impression Windows Forms
• Impression plus sécurisée dans Windows Forms