Stream.CanWrite 属性
当在派生类中重写时，获取指示当前流是否支持写入功能的值。
**命名空间:**System.IO
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
Public MustOverride ReadOnly Property CanWrite As Boolean
用法
Dim instance As Stream
Dim value As Boolean
value = instance.CanWrite
public abstract bool CanWrite { get; }
public:
virtual property bool CanWrite {
bool get () abstract;
}
/** @property */
public abstract boolean get_CanWrite ()
public abstract function get CanWrite () : boolean
属性值
如果流支持写入，为 true；否则为 false。
备注
有关创建文件和向文件中写入文本的示例，请参见 如何：向文件写入文本。有关从文件中读取文本的示例，请参见 如何：从文件读取文本。有关读取和写入二进制文件的示例，请参见 如何：对新建的数据文件进行读取和写入。
如果从 Stream 派生的类不支持写入，则调用 Write、BeginWrite 或 WriteByte 将引发 NotSupportedException。
如果该流已关闭，此属性将返回 false。
示例
下面是使用 CanWrite 属性的示例。
Imports System
Imports System.IO
Class TestRW
Public Shared Sub Main()
Dim fs As New FileStream("MyFile.txt", FileMode.OpenOrCreate, _
FileAccess.Write)
If fs.CanRead And fs.CanWrite Then
Console.WriteLine("MyFile.txt can be both written to and read from.")
Else
If fs.CanWrite Then
Console.WriteLine("MyFile.txt is writable.")
End If
End If
End Sub
End Class
'This code outputs "MyFile.txt is writable."
'To get the output message "MyFile.txt can be both written to and read from.",
'change the FileAccess parameter to ReadWrite in the FileStream constructor.
using System;
using System.IO;
class TestRW
{
public static void Main(String[] args)
{
FileStream fs = new FileStream("MyFile.txt", FileMode.OpenOrCreate,
FileAccess.Write);
if (fs.CanRead && fs.CanWrite) {
Console.WriteLine("MyFile.txt can be both written to and read from.");
}
else if (fs.CanWrite) {
Console.WriteLine("MyFile.txt is writable.");
}
}
}
//This code outputs "MyFile.txt is writable."
//To get the output message "MyFile.txt can be both written to and read from.",
//change the FileAccess parameter to ReadWrite in the FileStream constructor.
using namespace System;
using namespace System::IO;
int main()
{
FileStream^ fs = gcnew FileStream( "MyFile.txt",FileMode::OpenOrCreate,FileAccess::Write );
if ( fs->CanRead && fs->CanWrite )
{
Console::WriteLine( "MyFile.txt can be both written to and read from." );
}
else
if ( fs->CanWrite )
{
Console::WriteLine( "MyFile.txt is writable." );
}
}
//This code outputs "MyFile.txt is writable."
//To get the output message "MyFile.txt can be both written to and read from.",
//change the FileAccess parameter to ReadWrite in the FileStream constructor.
import System.*;
import System.IO.*;
class TestRW
{
public static void main(String[] args)
{
FileStream fs = new FileStream("MyFile.txt",
FileMode.OpenOrCreate, FileAccess.Write);
if (fs.get_CanRead() && fs.get_CanWrite()) {
Console.WriteLine(
"MyFile.txt can be both written to and read from.");
}
else {
if (fs.get_CanWrite()) {
Console.WriteLine("MyFile.txt is writable.");
}
}
} //main
} //TestRW
//This code outputs "MyFile.txt is writable."
//To get the output message "MyFile.txt can be both written to and read from.",
//change the FileAccess parameter to ReadWrite in the FileStream constructor.
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0
请参见
参考
Stream 类
Stream 成员
System.IO 命名空间