File.AppendText(String) 方法
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
建立會將 UTF-8 編碼的文字附加至現有檔案或新檔案 (如果指定的檔案不存在) 的 StreamWriter。
public:
static System::IO::StreamWriter ^ AppendText(System::String ^ path);public static System.IO.StreamWriter AppendText (string path);static member AppendText : string -> System.IO.StreamWriterPublic Shared Function AppendText (path As String) As StreamWriter參數
- path
- String
要附加至檔案的路徑。
傳回
資料流寫入器，會附加 UTF-8 編碼的文字至指定的檔案或新檔案。
例外狀況
呼叫端沒有必要的權限。
.NET Framework 和 2.1 之前的 .NET Core 版本：path是長度為零的字串、只包含空格符，或包含一或多個無效字元。 您可以使用 GetInvalidPathChars() 方法查詢無效字元。
path 為 null。
指定的路徑、檔案名稱，或兩者都超出系統定義的長度上限。
指定的路徑無效 (例如，此目錄不存在或位於未對應的磁碟機上)。
path 格式無效。
範例
下列範例會將文字附加至檔案。 如果檔案不存在，此方法會建立新的檔案。 不過，磁碟驅動器 C 上名為 temp 的目錄必須存在，範例才能順利完成。
using namespace System;
using namespace System::IO;
int main()
{
String^ path = "c:\\temp\\MyTest.txt";
// This text is added only once to the file.
if ( !File::Exists( path ) )
{
// Create a file to write to.
StreamWriter^ sw = File::CreateText( path );
try
{
sw->WriteLine( "Hello" );
sw->WriteLine( "And" );
sw->WriteLine( "Welcome" );
}
finally
{
if ( sw )
delete (IDisposable^)sw;
}
}
// This text is always added, making the file longer over time
// if it is not deleted.
StreamWriter^ sw = File::AppendText( path );
try
{
sw->WriteLine( "This" );
sw->WriteLine( "is Extra" );
sw->WriteLine( "Text" );
}
finally
{
if ( sw )
delete (IDisposable^)sw;
}
// Open the file to read from.
StreamReader^ sr = File::OpenText( path );
try
{
String^ s = "";
while ( s = sr->ReadLine() )
{
Console::WriteLine( s );
}
}
finally
{
if ( sr )
delete (IDisposable^)sr;
}
}
using System;
using System.IO;
class Test
{
public static void Main()
{
string path = @"c:\temp\MyTest.txt";
// This text is added only once to the file.
if (!File.Exists(path))
{
// Create a file to write to.
using (StreamWriter sw = File.CreateText(path))
{
sw.WriteLine("Hello");
sw.WriteLine("And");
sw.WriteLine("Welcome");
}
}
// This text is always added, making the file longer over time
// if it is not deleted.
using (StreamWriter sw = File.AppendText(path))
{
sw.WriteLine("This");
sw.WriteLine("is Extra");
sw.WriteLine("Text");
}
// Open the file to read from.
using (StreamReader sr = File.OpenText(path))
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
}
}
open System.IO
let path = @"c:\temp\MyTest.txt"
// This text is added only once to the file.
if File.Exists path |> not then
// Create a file to write to.
use sw = File.CreateText path
sw.WriteLine "Hello"
sw.WriteLine "And"
sw.WriteLine "Welcome"
// This text is always added, making the file longer over time
// if it is not deleted.
do
use sw = File.AppendText path
sw.WriteLine "This"
sw.WriteLine "is Extra"
sw.WriteLine "Text"
// Open the file to read from.
do
use sr = File.OpenText path
let mutable s = sr.ReadLine()
while isNull s |> not do
printfn $"{s}"
s <- sr.ReadLine()
Imports System.IO
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
' This text is added only once to the file.
If Not File.Exists(path) Then
' Create a file to write to.
Using sw As StreamWriter = File.CreateText(path)
sw.WriteLine("Hello")
sw.WriteLine("And")
sw.WriteLine("Welcome")
End Using
End If
' This text is always added, making the file longer over time
' if it is not deleted.
Using sw As StreamWriter = File.AppendText(path)
sw.WriteLine("This")
sw.WriteLine("is Extra")
sw.WriteLine("Text")
End Using
' Open the file to read from.
Using sr As StreamReader = File.OpenText(path)
Do While sr.Peek() >= 0
Console.WriteLine(sr.ReadLine())
Loop
End Using
End Sub
End Class
備註
這個方法相當於建 StreamWriter(String, Boolean) 構函式多載。 如果 指定的 path 檔案不存在，則會建立它。 如果檔案存在，請將作業寫入檔案的 StreamWriter 附加文字。 允許在檔案開啟時讀取其他線程。
允許 path 參數指定相對路徑或絕對路徑資訊。 相對路徑資訊會解譯為相對於目前的工作目錄。 若要取得目前的工作目錄，請參閱 GetCurrentDirectory。
參數 path 不區分大小寫。
如需一般 I/O 工作的清單，請參閱 一般 I/O 工作。
