Stream.CanWrite 属性
重要
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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。
public:
abstract property bool CanWrite { bool get(); };C#
public abstract bool CanWrite { get; }member this.CanWrite : boolPublic MustOverride ReadOnly Property CanWrite As Boolean如果流支持写入，则为 true；否则为 false。
下面是使用 CanWrite 属性的示例。
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.
C#
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.
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.
如果派生自 Stream 的类不支持写入，则对 Write、 BeginWrite或 WriteByte 的调用将 NotSupportedException引发 。 在这种情况下， Flush 通常实现为空方法，以确保与其他 Stream 类型完全兼容，因为刷新只读流是有效的。
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
