FileInfo.OpenWrite 方法

定义

命名空间:

System.IO

程序集:

System.Runtime.dll

Source:

FileInfo.cs

创建一个只写的 FileStream。

public:
 System::IO::FileStream ^ OpenWrite();

public System.IO.FileStream OpenWrite ();

member this.OpenWrite : unit -> System.IO.FileStream

Public Function OpenWrite () As FileStream

返回

FileStream

新的或现有文件的只写非共享的 FileStream 对象。

例外

UnauthorizedAccessException

创建 FileInfo 对象的实例时指定的路径为只读或是目录。

DirectoryNotFoundException

创建 FileInfo 对象的实例时指定的路径无效，例如此路径位于未映射的驱动器。

示例

以下示例打开一个文件进行写入，然后从该文件读取。

using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
   String^ path = "c:\\Temp\\MyTest.txt";
   FileInfo^ fi = gcnew FileInfo( path );

   // Open the stream for writing.
   {
      FileStream^ fs = fi->OpenWrite();
      try
      {
         array<Byte>^info = (gcnew UTF8Encoding( true ))->GetBytes( "This is to test the OpenWrite method." );
         
         // Add some information to the file.
         fs->Write( info, 0, info->Length );
      }
      finally
      {
         if ( fs )
            delete (IDisposable^)fs;
      }
   }
   
   // Open the stream and read it back.
   {
      FileStream^ fs = fi->OpenRead();
      try
      {
         array<Byte>^b = gcnew array<Byte>(1024);
         UTF8Encoding^ temp = gcnew UTF8Encoding( true );
         while ( fs->Read( b, 0, b->Length ) > 0 )
         {
            Console::WriteLine( temp->GetString( b ) );
         }
      }
      finally
      {
         if ( fs )
            delete (IDisposable^)fs;
      }
   }
}
//This code produces output similar to the following; 
//results may vary based on the computer/file structure/etc.:
//
//This is to test the OpenWrite method.
//
//
//
//
//
//
//
//
//
//
//
//

using System;
using System.IO;
using System.Text;

class Test
{
    public static void Main()
    {
        string path = @"c:\Temp\MyTest.txt";
        FileInfo fi = new FileInfo(path);

        // Open the stream for writing.
        using (FileStream fs = fi.OpenWrite())
        {
            Byte[] info =
                new UTF8Encoding(true).GetBytes("This is to test the OpenWrite method.");

            // Add some information to the file.
            fs.Write(info, 0, info.Length);
        }

        // Open the stream and read it back.
        using (FileStream fs = fi.OpenRead())
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while (fs.Read(b,0,b.Length) > 0)
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }
}
//This code produces output similar to the following;
//results may vary based on the computer/file structure/etc.:
//
//This is to test the OpenWrite method.
//
//
//
//
//
//
//
//
//
//
//

Imports System.IO
Imports System.Text

Public Class Test
    Public Shared Sub Main()
        Dim path As String = "c:\Temp\MyTest.txt"
        Dim fi As FileInfo = New FileInfo(path)
        Dim fs As FileStream

        ' Open the stream for writing.
        fs = fi.OpenWrite()
        Dim info As Byte() = _
            New UTF8Encoding(True).GetBytes("This is to test the OpenWrite method.")

        ' Add some information to the file.
        fs.Write(info, 0, info.Length)
        fs.Close()

        'Open the stream and read it back.
        fs = fi.OpenRead()
        Dim b(1023) As Byte
        Dim temp As UTF8Encoding = New UTF8Encoding(True)

        Do While fs.Read(b, 0, b.Length) > 0
            Console.WriteLine(temp.GetString(b))
        Loop
        fs.Close()
    End Sub
End Class
'This code produces output similar to the following; 
'results may vary based on the computer/file structure/etc.:
'
'This is to test the OpenWrite method.
'
'
'
'
'
'
'
'
'
'
'
'

注解

如果文件路径中已存在文件，方法 OpenWrite 会打开一个文件;如果文件不存在，则创建一个新文件。 对于现有文件，它不会将新文本追加到现有文本。 相反，它会用新字符覆盖现有字符。 如果使用较短的字符串 (（如“第二次运行”) ）覆盖较长的字符串 (“这是 OpenWrite 方法的测试”) ，则该文件将包含 (“OpenWrite 方法的第二次运行测试”) 的混合字符串。