How to: Print in Windows Forms Using Print Preview

Artikel
02/06/2023

It is very common in Windows Forms programming to offer print preview in addition to printing services. An easy way to add print preview services to your application is to use a PrintPreviewDialog control in combination with the PrintPage event-handling logic for printing a file.

To preview a text document with a PrintPreviewDialog control

Add a PrintPreviewDialog, PrintDocument, and two strings to your form.

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

Set the DocumentName property to the document you wish to print, and open and read the document's contents to the string you added previously.

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

As you would for printing the document, in the PrintPage event handler, use the Graphics property of the PrintPageEventArgs class and the file contents to calculate lines per page and render the document's contents. After each page is drawn, check to see if it is the last page, and set the HasMorePages property of the PrintPageEventArgs accordingly. The PrintPage event is raised until HasMorePages is false. When the document has finished rendering, reset the string to be rendered. Also, make sure the PrintPage event is associated with its event-handling method.

Note

You may have already completed steps 2 and 3 if you have implemented printing in your application.

In the following code example, the event handler is used to print the "testPage.txt" file in the same font used on the form.

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

Set the Document property of the PrintPreviewDialog control to the PrintDocument component on the form.
```
printPreviewDialog1.Document = printDocument1;
```
```
printPreviewDialog1.Document = printDocument1
```
Call the ShowDialog method on the PrintPreviewDialog control. You would typically call ShowDialog from the Click event-handling method of a button. Calling ShowDialog raises the PrintPage event and renders the output to the PrintPreviewDialog control. When the user clicks the print icon on the dialog, the PrintPage event is raised again, sending the output to the printer instead of the preview dialog. This is why the string is reset at the end of the rendering process in step 3.

The following code example shows the Click event-handling method for a button on the form. This event-handling method calls the methods to read the document and show the print preview dialog.
```
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
```

Example

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

Compiling the Code

This example requires:

References to the System, System.Windows.Forms, System.Drawing assemblies.

Dela via

How to: Print in Windows Forms Using Print Preview

To preview a text document with a PrintPreviewDialog control

Example

Compiling the Code

See also

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