如何:使用 OpenFileDialog 開啟檔案
元件 System.Windows.Forms.OpenFileDialog 會開啟 Windows 對話方塊來流覽和選取檔案。 若要開啟並讀取選取的檔案,您可以使用 OpenFileDialog.OpenFile 方法,或建立 類別的 System.IO.StreamReader 實例。 下列範例顯示這兩種方法。
在 .NET Framework 中,若要取得或設定 FileName 屬性,需要 類別授 System.Security.Permissions.FileIOPermission 與的許可權等級。 這些範例會 FileIOPermission 執行許可權檢查,而且在部分信任內容中執行時,可能會因為許可權不足而擲回例外狀況。 如需詳細資訊,請參閱 程式碼存取安全性基本概念 。
您可以從 C# 或 Visual Basic 命令列建置並執行這些範例作為 .NET Framework 應用程式。 如需詳細資訊,請參閱 使用 csc.exe 建置命令列或 從命令列 建置。
從 .NET Core 3.0 開始,您也可以從具有 .NET Core Windows Forms < 資料夾 name.csproj > 專案檔的資料夾建置和執行範例作為 Windows .NET Core 應用程式。
範例:使用 StreamReader 將檔案讀取為數據流
下列範例會使用 Windows Forms Button 控制項的 Click 事件處理常式,以 ShowDialog 方法開啟 OpenFileDialog 。 使用者選擇檔案並選取 [確定 ] 之後,類別的 StreamReader 實例會讀取檔案,並在表單的文字方塊中顯示其內容。 如需從檔案資料流程讀取的詳細資訊,請參閱 FileStream.BeginRead 和 FileStream.Read 。
using System;
using System.Drawing;
using System.IO;
using System.Security;
using System.Windows.Forms;
public class OpenFileDialogForm : Form
{
[STAThread]
public static void Main()
{
Application.SetCompatibleTextRenderingDefault(false);
Application.EnableVisualStyles();
Application.Run(new OpenFileDialogForm());
}
private Button selectButton;
private OpenFileDialog openFileDialog1;
private TextBox textBox1;
public OpenFileDialogForm()
{
openFileDialog1 = new OpenFileDialog();
selectButton = new Button
{
Size = new Size(100, 20),
Location = new Point(15, 15),
Text = "Select file"
};
selectButton.Click += new EventHandler(SelectButton_Click);
textBox1 = new TextBox
{
Size = new Size(300, 300),
Location = new Point(15, 40),
Multiline = true,
ScrollBars = ScrollBars.Vertical
};
ClientSize = new Size(330, 360);
Controls.Add(selectButton);
Controls.Add(textBox1);
}
private void SetText(string text)
{
textBox1.Text = text;
}
private void SelectButton_Click(object sender, EventArgs e)
{
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
try
{
var sr = new StreamReader(openFileDialog1.FileName);
SetText(sr.ReadToEnd());
}
catch (SecurityException ex)
{
MessageBox.Show($"Security error.\n\nError message: {ex.Message}\n\n" +
$"Details:\n\n{ex.StackTrace}");
}
}
}
}
Imports System.Drawing
Imports System.IO
Imports System.Security
Imports System.Windows.Forms
Public Class OpenFileDialogForm : Inherits Form
Public Shared Sub Main()
Application.SetCompatibleTextRenderingDefault(False)
Application.EnableVisualStyles()
Dim frm As New OpenFileDialogForm()
Application.Run(frm)
End Sub
Dim WithEvents SelectButton As Button
Dim openFileDialog1 As OpenFileDialog
Dim TextBox1 As TextBox
Private Sub New()
ClientSize = New Size(400, 400)
openFileDialog1 = New OpenFileDialog()
SelectButton = New Button()
With SelectButton
.Text = "Select file"
.Location = New Point(15, 15)
.Size = New Size(100, 25)
End With
TextBox1 = New TextBox()
With TextBox1
.Size = New Size(300, 300)
.Location = New Point(15, 50)
.Multiline = True
.ScrollBars = ScrollBars.Vertical
End With
Controls.Add(SelectButton)
Controls.Add(TextBox1)
End Sub
Private Sub SetText(text)
TextBox1.Text = text
End Sub
Public Sub SelectButton_Click(sender As Object, e As EventArgs) _
Handles SelectButton.Click
If openFileDialog1.ShowDialog() = DialogResult.OK Then
Try
Dim sr As New StreamReader(openFileDialog1.FileName)
SetText(sr.ReadToEnd())
Catch SecEx As SecurityException
MessageBox.Show($"Security error:{vbCrLf}{vbCrLf}{SecEx.Message}{vbCrLf}{vbCrLf}" &
$"Details:{vbCrLf}{vbCrLf}{SecEx.StackTrace}")
End Try
End If
End Sub
End Class
範例:使用 OpenFile 從篩選的選取範圍開啟檔案
下列範例會使用 Button 控制項的事件處理常式,以只顯示文字檔的 Click 篩選來開啟 OpenFileDialog 。 使用者選擇文字檔並選取 [ 確定 ] 之後, OpenFile 方法會用來在 記事本中開啟檔案。
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Security;
using System.Windows.Forms;
public class OpenFileDialogForm : Form
{
[STAThread]
public static void Main()
{
Application.SetCompatibleTextRenderingDefault(false);
Application.EnableVisualStyles();
Application.Run(new OpenFileDialogForm());
}
private Button selectButton;
private OpenFileDialog openFileDialog1;
public OpenFileDialogForm()
{
openFileDialog1 = new OpenFileDialog()
{
FileName = "Select a text file",
Filter = "Text files (*.txt)|*.txt",
Title = "Open text file"
};
selectButton = new Button()
{
Size = new Size(100, 20),
Location = new Point(15, 15),
Text = "Select file"
};
selectButton.Click += new EventHandler(selectButton_Click);
Controls.Add(selectButton);
}
private void selectButton_Click(object sender, EventArgs e)
{
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
try
{
var filePath = openFileDialog1.FileName;
using (Stream str = openFileDialog1.OpenFile())
{
Process.Start("notepad.exe", filePath);
}
}
catch (SecurityException ex)
{
MessageBox.Show($"Security error.\n\nError message: {ex.Message}\n\n" +
$"Details:\n\n{ex.StackTrace}");
}
}
}
}
Imports System.ComponentModel
Imports System.Diagnostics
Imports System.IO
Imports System.Security
Imports System.Windows.Forms
Public Class OpenFileDialogForm : Inherits Form
Dim WithEvents selectButton As Button
Dim openFileDialog1 As OpenFileDialog
Public Shared Sub Main()
Application.SetCompatibleTextRenderingDefault(false)
Application.EnableVisualStyles()
Dim frm As New OpenFileDialogForm()
Application.Run(frm)
End Sub
Private Sub New()
openFileDialog1 = New OpenFileDialog() With
{
.FileName = "Select a text file",
.Filter = "Text files (*.txt)|*.txt",
.Title = "Open text file"
}
selectButton = New Button() With {.Text = "Select file"}
Controls.Add(selectButton)
End Sub
Public Sub selectButton_Click(sender As Object, e As EventArgs) _
Handles selectButton.Click
If OpenFileDialog1.ShowDialog() = DialogResult.OK Then
Try
Dim filePath = OpenFileDialog1.FileName
Using str = openFileDialog1.OpenFile()
Process.Start("notepad.exe", filePath)
End Using
Catch SecEx As SecurityException
MessageBox.Show($"Security error:{vbCrLf}{vbCrLf}{SecEx.Message}{vbCrLf}{vbCrLf}" &
$"Details:{vbCrLf}{vbCrLf}{SecEx.StackTrace}")
End Try
End If
End Sub
End Class
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