FileDialog.DefaultExt 属性

定义

获取或设置默认文件扩展名。Gets or sets the default file name extension.

public:
 property System::String ^ DefaultExt { System::String ^ get(); void set(System::String ^ value); };
public string DefaultExt { get; set; }
member this.DefaultExt : string with get, set
Public Property DefaultExt As String

属性值

默认的文件扩展名。The default file name extension. 返回的字符串不包含句点。The returned string does not include the period. 默认值为空字符串 ("")。The default value is an empty string ("").

示例

下面的代码示例演示如何将 RichTextBox.SaveFileRichTextBox.LoadFile 方法与流一起使用。The following code example demonstrates using the RichTextBox.SaveFile and RichTextBox.LoadFile methods with streams. 它还演示了如何使用 FileNameDefaultExtSaveFileDialog.CreatePromptSaveFileDialog.OverwritePrompt 成员。It also demonstrates using the FileName, DefaultExt, SaveFileDialog.CreatePrompt, and SaveFileDialog.OverwritePrompt members.

这是一个完整的示例,可以在将其复制到项目时运行。This is a complete example that is ready to run when you copy it to your project.

using namespace System;
using namespace System::Drawing;
using namespace System::IO;
using namespace System::Windows::Forms;

public ref class Form1: public Form
{
public private:
   RichTextBox^ RichTextBox1;
   Button^ Button1;
   RichTextBox^ RichTextBox2;
   Button^ Button2;
   SaveFileDialog^ SaveFileDialog1;

public:
   Form1()
      : Form()
   {
      userInput = gcnew MemoryStream;
      this->RichTextBox1 = gcnew RichTextBox;
      this->Button1 = gcnew Button;
      this->RichTextBox2 = gcnew RichTextBox;
      this->Button2 = gcnew Button;
      this->SaveFileDialog1 = gcnew SaveFileDialog;
      this->SuspendLayout();
      this->RichTextBox1->Location = Point( 24, 64 );
      this->RichTextBox1->Name = "RichTextBox1";
      this->RichTextBox1->TabIndex = 0;
      this->RichTextBox1->Text = "Type something here.";
      this->Button1->Location = Point( 96, 16 );
      this->Button1->Name = "Button1";
      this->Button1->Size = Size( 96, 24 );
      this->Button1->TabIndex = 1;
      this->Button1->Text = "Save To Stream";
      this->Button1->Click += 
          gcnew EventHandler( this, &Form1::Button1_Click );
      this->RichTextBox2->Location = Point( 152, 64 );
      this->RichTextBox2->Name = "RichTextBox2";
      this->RichTextBox2->TabIndex = 3;
      this->RichTextBox2->Text = "It will be added to the stream "
      "and appear here.";
      this->Button2->Location = Point( 104, 200 );
      this->Button2->Name = "Button2";
      this->Button2->Size = Size( 88, 32 );
      this->Button2->TabIndex = 4;
      this->Button2->Text = "Save Stream To File";
      this->Button2->Click += 
          gcnew EventHandler( this, &Form1::Button2_Click );
      this->ClientSize = Size( 292, 266 );
      this->Controls->Add( this->Button2 );
      this->Controls->Add( this->RichTextBox2 );
      this->Controls->Add( this->Button1 );
      this->Controls->Add( this->RichTextBox1 );
      this->Name = "Form1";
      this->Text = "Form1";
      this->ResumeLayout( false );
   }

   // Declare a new memory stream.
   MemoryStream^ userInput;

private:

   // Save the content of RichTextBox1 to the memory stream, 
   // appending a LineFeed character.  
   void Button1_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      RichTextBox1->SaveFile( userInput, RichTextBoxStreamType::PlainText );
      userInput->WriteByte( 13 );
      
      // Display the entire contents of the stream,
      // by setting its position to 0, to RichTextBox2.
      userInput->Position = 0;
      RichTextBox2->LoadFile( userInput, RichTextBoxStreamType::PlainText );
   }


   // Shows the use of a SaveFileDialog to save a MemoryStream to a file.
   void Button2_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      
      // Set the properties on SaveFileDialog1 so the user is 
      // prompted to create the file if it doesn't exist 
      // or overwrite the file if it does exist.
      SaveFileDialog1->CreatePrompt = true;
      SaveFileDialog1->OverwritePrompt = true;
      
      // Set the file name to myText.txt, set the type filter
      // to text files, and set the initial directory to the
      // MyDocuments folder.
      SaveFileDialog1->FileName = "myText";
      // DefaultExt is only used when "All files" is selected from 
      // the filter box and no extension is specified by the user.
      SaveFileDialog1->DefaultExt = "txt";
      SaveFileDialog1->Filter = "Text files (*.txt)|*.txt|All files (*.*)|*.*";
      SaveFileDialog1->InitialDirectory = 
          Environment->GetFolderPath(Environment::SpecialFolder::MyDocuments);
      
      // Call ShowDialog and check for a return value of DialogResult.OK,
      // which indicates that the file was saved. 
      DialogResult result = SaveFileDialog1->ShowDialog();
      Stream^ fileStream;
      if ( result == DialogResult::OK )
      {
         fileStream = SaveFileDialog1->OpenFile();
         userInput->Position = 0;
         userInput->WriteTo( fileStream );
         fileStream->Close();
      }
   }
};

int main()
{
   Application::Run( gcnew Form1 );
}

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

public partial class Form1: Form
{
    internal RichTextBox RichTextBox1;
    internal Button Button1;
    internal RichTextBox RichTextBox2;
    internal Button Button2;
    internal SaveFileDialog SaveFileDialog1;

    public Form1() : base()
    {   
        this.RichTextBox1 = new RichTextBox();
        this.Button1 = new Button();
        this.RichTextBox2 = new RichTextBox();
        this.Button2 = new Button();
        this.SaveFileDialog1 = new SaveFileDialog();
        this.SuspendLayout();
        this.RichTextBox1.Location = new Point(24, 64);
        this.RichTextBox1.Name = "RichTextBox1";
        this.RichTextBox1.TabIndex = 0;
        this.RichTextBox1.Text = "Type something here.";
        this.Button1.Location = new Point(96, 16);
        this.Button1.Name = "Button1";
        this.Button1.Size = new Size(96, 24);
        this.Button1.TabIndex = 1;
        this.Button1.Text = "Save To Stream";
        this.Button1.Click += new EventHandler(Button1_Click);
        this.RichTextBox2.Location = new Point(152, 64);
        this.RichTextBox2.Name = "RichTextBox2";
        this.RichTextBox2.TabIndex = 3;
        this.RichTextBox2.Text = 
            "It will be added to the stream and appear here.";
        this.Button2.Location = new Point(104, 200);
        this.Button2.Name = "Button2";
        this.Button2.Size = new Size(88, 32);
        this.Button2.TabIndex = 4;
        this.Button2.Text = "Save Stream To File";
        this.Button2.Click += new EventHandler(Button2_Click);
        this.ClientSize = new Size(292, 266);
        this.Controls.Add(this.Button2);
        this.Controls.Add(this.RichTextBox2);
        this.Controls.Add(this.Button1);
        this.Controls.Add(this.RichTextBox1);
        this.Name = "Form1";
        this.Text = "Form1";
        this.ResumeLayout(false);
    }

    public static void Main()
    {
        Application.Run(new Form1());
    }

    // Declare a new memory stream.
    MemoryStream userInput = new MemoryStream();

    // Save the content of RichTextBox1 to the memory stream, 
    // appending a LineFeed character.  
    private void Button1_Click(Object sender, EventArgs e)
    {
        RichTextBox1.SaveFile(userInput, RichTextBoxStreamType.PlainText);
        userInput.WriteByte(13);

        // Display the entire contents of the stream,
        // by setting its position to 0, to RichTextBox2.
        userInput.Position = 0;
        RichTextBox2.LoadFile(userInput, RichTextBoxStreamType.PlainText);
    }

    // Shows the use of a SaveFileDialog to save a MemoryStream to a file.
    private void Button2_Click(Object sender, EventArgs e)
    {
        // Set the properties on SaveFileDialog1 so the user is 
        // prompted to create the file if it doesn't exist 
        // or overwrite the file if it does exist.
        SaveFileDialog1.CreatePrompt = true;
        SaveFileDialog1.OverwritePrompt = true;

        // Set the file name to myText.txt, set the type filter
        // to text files, and set the initial directory to the 
        // MyDocuments folder.
        SaveFileDialog1.FileName = "myText";
        // DefaultExt is only used when "All files" is selected from 
        // the filter box and no extension is specified by the user.
        SaveFileDialog1.DefaultExt = "txt";
        SaveFileDialog1.Filter = 
            "Text files (*.txt)|*.txt|All files (*.*)|*.*";
        SaveFileDialog1.InitialDirectory = 
            Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        // Call ShowDialog and check for a return value of DialogResult.OK,
        // which indicates that the file was saved. 
        DialogResult result = SaveFileDialog1.ShowDialog();
        Stream fileStream;

        if (result == DialogResult.OK)
        {
            // Open the file, copy the contents of memoryStream to fileStream,
            // and close fileStream. Set the memoryStream.Position value to 0 
            // to copy the entire stream. 
            fileStream = SaveFileDialog1.OpenFile();
            userInput.Position = 0;
            userInput.WriteTo(fileStream);
            fileStream.Close();
        }
    }
}
Imports System.Drawing
Imports System.IO
Imports System.Windows.Forms

Partial Public Class Form1
    Inherits Form

    Friend WithEvents RichTextBox1 As RichTextBox
    Friend WithEvents Button1 As Button
    Friend WithEvents RichTextBox2 As RichTextBox
    Friend WithEvents Button2 As Button
    Friend WithEvents SaveFileDialog1 As SaveFileDialog

    Public Sub New()
        MyBase.New()
        Me.RichTextBox1 = New RichTextBox
        Me.Button1 = New Button
        Me.RichTextBox2 = New RichTextBox
        Me.Button2 = New Button
        Me.SaveFileDialog1 = New SaveFileDialog
        Me.SuspendLayout()
        Me.RichTextBox1.Location = New Point(24, 64)
        Me.RichTextBox1.Name = "RichTextBox1"
        Me.RichTextBox1.TabIndex = 0
        Me.RichTextBox1.Text = "Type something here."
        Me.Button1.Location = New Point(96, 16)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New Size(96, 24)
        Me.Button1.TabIndex = 1
        Me.Button1.Text = "Save To Stream"
        Me.RichTextBox2.Location = New Point(152, 64)
        Me.RichTextBox2.Name = "RichTextBox2"
        Me.RichTextBox2.TabIndex = 3
        Me.RichTextBox2.Text = "It will be added to the stream and appear here."
        Me.Button2.Location = New Point(104, 200)
        Me.Button2.Name = "Button2"
        Me.Button2.Size = New Size(88, 32)
        Me.Button2.TabIndex = 4
        Me.Button2.Text = "Save Stream To File"
        Me.ClientSize = New Size(292, 266)
        Me.Controls.Add(Me.Button2)
        Me.Controls.Add(Me.RichTextBox2)
        Me.Controls.Add(Me.Button1)
        Me.Controls.Add(Me.RichTextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

    Public Shared Sub Main()
        Application.Run(New Form1)
    End Sub

    ' Declare a new memory stream.
    Dim userInput As New MemoryStream

    ' Save the content of RichTextBox1 to the memory stream, appending
    'a LineFeed character.  
    Private Sub Button1_Click(ByVal sender As Object, _
        ByVal e As EventArgs) Handles Button1.Click
        RichTextBox1.SaveFile(userInput, RichTextBoxStreamType.PlainText)
        userInput.WriteByte(13)

        ' Display the entire contents of the stream,
        ' by setting its position to 0, to RichTextBox2.
        userInput.Position = 0
        RichTextBox2.LoadFile(userInput, RichTextBoxStreamType.PlainText)
    End Sub

    ' Shows the use of a SaveFileDialog to save a MemoryStream to a file.
    Private Sub Button2_Click(ByVal sender As Object, _
        ByVal e As EventArgs) Handles Button2.Click

        ' Set the properties on SaveFileDialog1 so the user is 
        ' prompted to create the file if it doesn't exist 
        ' or overwrite the file if it does exist.
        SaveFileDialog1.CreatePrompt = True
        SaveFileDialog1.OverwritePrompt = True

        ' Set the file name to myText.txt, set the type filter
        ' to text files, and set the initial directory to the 
        ' MyDocuments folder.
        SaveFileDialog1.FileName = "myText"
        ' DefaultExt is only used when "All files" is selected from 
        ' the filter box and no extension is specified by the user.
        SaveFileDialog1.DefaultExt = "txt"
        SaveFileDialog1.Filter = "Text files (*.txt)|*.txt|All files (*.*)|*.*"
        SaveFileDialog1.InitialDirectory = _
            Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

        ' Call ShowDialog and check for a return value of DialogResult.OK,
        ' which indicates that the file was saved. 
        Dim result As DialogResult = SaveFileDialog1.ShowDialog()
        Dim fileStream As Stream

        If (result = DialogResult.OK) Then
            ' Open the file, copy the contents of memoryStream to fileStream,
            ' and close fileStream. Set the memoryStream.Position value to 0 to 
            ' copy the entire stream. 
            fileStream = SaveFileDialog1.OpenFile()
            userInput.Position = 0
            userInput.WriteTo(fileStream)
            fileStream.Close()
        End If
    End Sub

End Class

注解

当应用程序的用户指定一个不带扩展名的文件名时,FileDialog 会将扩展名附加到文件名。When the user of your application specifies a file name without an extension, the FileDialog appends an extension to the file name. 使用的扩展由 FilterDefaultExt 属性确定。The extension that is used is determined by the Filter and DefaultExt properties. 如果在 FileDialog 中选择了筛选器,并且筛选器指定了扩展,则使用该扩展。If a filter is selected in the FileDialog and the filter specifies an extension, then that extension is used. 如果所选筛选器使用通配符代替扩展,则使用 DefaultExt 属性中指定的扩展。If the filter selected uses a wildcard in place of the extension, then the extension specified in the DefaultExt property is used.

适用于