StreamingContextStates 枚举

定义一个标记集，用于在序列化过程中指定流的源或目标上下文。

此枚举有一个 FlagsAttribute 属性，允许其成员值按位组合。

**命名空间:**System.Runtime.Serialization
**程序集:**mscorlib（在 mscorlib.dll 中）

语法

声明
<SerializableAttribute> _
<FlagsAttribute> _
<ComVisibleAttribute(True)> _
Public Enumeration StreamingContextStates
用法
Dim instance As StreamingContextStates

[SerializableAttribute] 
[FlagsAttribute] 
[ComVisibleAttribute(true)] 
public enum StreamingContextStates

[SerializableAttribute] 
[FlagsAttribute] 
[ComVisibleAttribute(true)] 
public enum class StreamingContextStates

/** @attribute SerializableAttribute() */ 
/** @attribute FlagsAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public enum StreamingContextStates

SerializableAttribute 
FlagsAttribute 
ComVisibleAttribute(true) 
public enum StreamingContextStates

成员

	成员名称	说明
	All	指定可以向其他任何上下文传输（或从其他任何上下文接收）序列化数据。
	Clone	指定对象图形正在进行克隆。用户可以假定克隆图形将继续在同一进程中存在，可以安全地访问句柄或其他对非托管资源的引用。
	CrossAppDomain	指定源或目标上下文是另外一个 AppDomain。（有关 AppDomain 的说明，请参见 应用程序域）。
	CrossMachine	指定源或目标上下文是另外一台计算机。
	CrossProcess	指定源或目标上下文是同一计算机上的另外一个进程。
	File	指定源或目标上下文是文件。用户可以假定文件的持续时间长于创建它们的进程，并且文件以特定方式将对象序列化，此方式不会使反序列化进程要求访问当前进程中的任何数据。
	Other	指定序列化上下文未知。
	Persistence	指定源或目的上下文是持续的存储区，它可以包括数据库、文件或其他后备存储区。用户可以假定持续数据的持续时间长于创建数据的进程，并且持续数据以特定方式将对象序列化，此方式不会使反序列化进程要求访问当前进程中的任何数据。
	Remoting	指定数据在未知位置的上下文中进行远程处理。用户无法假定它是否在同一台计算机上。

示例

下面的代码示例演示了 StreamingContextStates 枚举的用法。

Imports System
Imports System.IO
Imports System.Collections
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Runtime.Serialization
Imports System.Runtime.InteropServices
Imports System.Security.Permissions

<Assembly: SecurityPermission( _
SecurityAction.RequestMinimum, Execution:=True)> 
' This class includes several Win32 interop definitions.
Friend Class Win32
    Public Shared ReadOnly InvalidHandleValue As New IntPtr(-1)
    Public Const FILE_MAP_WRITE As Int32 = 2
    Public Const PAGE_READWRITE As Int32 = &H4

    <DllImport("Kernel32")> _
    Public Shared Function CreateFileMapping(ByVal hFile As IntPtr, _
                                             ByVal pAttributes As IntPtr, _
                                             ByVal flProtect As Int32, _
                                             ByVal dwMaximumSizeHigh As Int32, _
                                             ByVal dwMaximumSizeLow As Int32, _
                                             ByVal pName As String) As IntPtr
    End Function

    <DllImport("Kernel32")> _
    Public Shared Function OpenFileMapping(ByVal dwDesiredAccess As Int32, _
                                           ByVal bInheritHandle As Boolean, _
                                           ByVal name As String) As IntPtr
    End Function

    <DllImport("Kernel32")> _
    Public Shared Function CloseHandle(ByVal handle As IntPtr) As Boolean
    End Function

    <DllImport("Kernel32")> _
    Public Shared Function MapViewOfFile(ByVal hFileMappingObject As IntPtr, _
                                         ByVal dwDesiredAccess As Int32, _
                                         ByVal dwFileOffsetHigh As Int32, _
                                         ByVal dwFileOffsetLow As Int32, _
                                         ByVal dwNumberOfBytesToMap As IntPtr) _
                                         As IntPtr
    End Function

    <DllImport("Kernel32")> _
    Public Shared Function UnmapViewOfFile(ByVal address As IntPtr) As Boolean
    End Function

    <DllImport("Kernel32")> _
    Public Shared Function DuplicateHandle(ByVal hSourceProcessHandle As IntPtr, _
                                           ByVal hSourceHandle As IntPtr, _
                                           ByVal hTargetProcessHandle As IntPtr, _
                                           ByRef lpTargetHandle As IntPtr, _
                                           ByVal dwDesiredAccess As Int32, _
                                           ByVal bInheritHandle As Boolean, _
                                           ByVal dwOptions As Int32) As Boolean
    End Function

    Public Const DUPLICATE_CLOSE_SOURCE As Int32 = &H1
    Public Const DUPLICATE_SAME_ACCESS As Int32 = &H2

    <DllImport("Kernel32")> Public Shared Function GetCurrentProcess() As IntPtr
    End Function
End Class


' This class wraps memory that can be simultaneously 
' shared by multiple AppDomains and Processes.
<Serializable()> Public NotInheritable Class SharedMemory
    Implements ISerializable
    Implements IDisposable

    ' The handle and string that identify 
    ' the Windows file-mapping object.
    Private m_hFileMap As IntPtr = IntPtr.Zero
    Private m_name As String

    ' The address of the memory-mapped file-mapping object.
    Private m_address As IntPtr
    <SecurityPermissionAttribute(SecurityAction.LinkDemand, _
    Flags:=SecurityPermissionFlag.UnmanagedCode)> _
    Public Function GetByte(ByVal offset As Int32) As Byte
        Dim b(0) As Byte
        Marshal.Copy(New IntPtr(m_address.ToInt64() + offset), b, 0, 1)
        Return b(0)
    End Function

    <SecurityPermissionAttribute(SecurityAction.LinkDemand, _
    Flags:=SecurityPermissionFlag.UnmanagedCode)> _
    Public Sub SetByte(ByVal offset As Int32, ByVal value As Byte)
        Dim b(0) As Byte
        b(0) = value
        Marshal.Copy(b, 0, New IntPtr(m_address.ToInt64() + offset), 1)
    End Sub


    ' The constructors.
    Public Sub New(ByVal size As Int32)
        Me.New(size, Nothing)
    End Sub

    Public Sub New(ByVal size As Int32, ByVal name As String)
        m_hFileMap = Win32.CreateFileMapping(Win32.InvalidHandleValue, _
           IntPtr.Zero, Win32.PAGE_READWRITE, 0, size, name)
        If (m_hFileMap.Equals(IntPtr.Zero)) Then _
           Throw New Exception("Could not create memory-mapped file.")
        m_name = name
        m_address = Win32.MapViewOfFile(m_hFileMap, _
           Win32.FILE_MAP_WRITE, 0, 0, IntPtr.Zero)
    End Sub


    ' The cleanup methods.
    Public Sub Dispose() Implements IDisposable.Dispose
        GC.SuppressFinalize(Me)
        Dispose(True)
    End Sub

    Private Sub Dispose(ByVal disposing As Boolean)
        Win32.UnmapViewOfFile(m_address)
        Win32.CloseHandle(m_hFileMap)
        m_address = IntPtr.Zero
        m_hFileMap = IntPtr.Zero
    End Sub

    Protected Overrides Sub Finalize()
        Dispose(False)
    End Sub


    ' Private helper methods.
    Private Shared Function AllFlagsSet(ByVal flags As Int32, _
                                        ByVal flagsToTest As Int32) As Boolean
        Return (flags And flagsToTest) = flagsToTest
    End Function

    Private Shared Function AnyFlagsSet(ByVal flags As Int32, _
                                        ByVal flagsToTest As Int32) As Boolean
        Return (flags And flagsToTest) <> 0
    End Function


    ' The security attribute demands that code that calls  
    ' this method have permission to perform serialization.
    <SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter:=True)> _
    Sub GetObjectData(ByVal info As SerializationInfo, _
                      ByVal context As StreamingContext) _
                      Implements ISerializable.GetObjectData
        ' The context's State member indicates where the object will be deserialized.

        ' A SharedMemory object cannot be serialized 
        ' to any of the following destinations.
        Const InvalidDestinations As StreamingContextStates = _
           StreamingContextStates.CrossMachine Or _
           StreamingContextStates.File Or _
           StreamingContextStates.Other Or _
           StreamingContextStates.Persistence Or _
           StreamingContextStates.Remoting
        If AnyFlagsSet(CType(context.State, Int32), _
                       CType(InvalidDestinations, Int32)) Then
            Throw New SerializationException("The SharedMemory object " & _
               "cannot be serialized to any of the following streaming contexts: " _
               & InvalidDestinations)
        End If

        Const DeserializableByHandle As StreamingContextStates = _
                 StreamingContextStates.Clone Or _
                 StreamingContextStates.CrossAppDomain

        If AnyFlagsSet(CType(context.State, Int32), _
              CType(DeserializableByHandle, Int32)) Then
            info.AddValue("hFileMap", m_hFileMap)
        End If

        Const DeserializableByName As StreamingContextStates = _
                 StreamingContextStates.CrossProcess   ' The same computer.
        If AnyFlagsSet(CType(context.State, Int32), CType(DeserializableByName, _
                       Int32)) Then
            If m_name = Nothing Then
                Throw New SerializationException("The SharedMemory object " & _
                   "cannot be serialized CrossProcess because it was not constructed " & _
                   "with a String name.")
            End If
            info.AddValue("name", m_name)
        End If
    End Sub

    Private Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)
        ' The context's State member indicates where the object was serialized from.

        Const InvalidSources As StreamingContextStates = _
                 StreamingContextStates.CrossMachine Or _
                 StreamingContextStates.File Or _
                 StreamingContextStates.Other Or _
                 StreamingContextStates.Persistence Or _
                 StreamingContextStates.Remoting

        If AnyFlagsSet(CType(context.State, Int32), CType(InvalidSources, Int32)) Then
            Throw New SerializationException("The SharedMemory object " & _
               "cannot be deserialized from any of the following stream contexts: " & _
               InvalidSources)
        End If

        Const SerializedByHandle As StreamingContextStates = _
                 StreamingContextStates.Clone Or _
                 StreamingContextStates.CrossAppDomain ' The same process.
        If AnyFlagsSet(CType(context.State, Int32), _
              CType(SerializedByHandle, Int32)) Then
            Try
                Win32.DuplicateHandle(Win32.GetCurrentProcess(), _
                   CType(info.GetValue("hFileMap", GetType(IntPtr)), IntPtr), _
                      Win32.GetCurrentProcess(), m_hFileMap, 0, False, _
                      Win32.DUPLICATE_SAME_ACCESS)
            Catch e As SerializationException
                Throw New SerializationException("A SharedMemory was not " & _
                   "serialized using any of the following streaming contexts: " & _
                   SerializedByHandle)
            End Try
        End If

        Const SerializedByName As StreamingContextStates = _
                 StreamingContextStates.CrossProcess   ' The same computer.
        If AnyFlagsSet(CType(context.State, Int32), _
                       CType(SerializedByName, Int32)) Then
            Try
                m_name = info.GetString("name")
            Catch e As SerializationException
                Throw New SerializationException("A SharedMemory object " & _
                   "was not serialized using any of the following streaming contexts: " & _
                   SerializedByName)
            End Try
            m_hFileMap = Win32.OpenFileMapping(Win32.FILE_MAP_WRITE, False, m_name)
        End If
        If Not m_hFileMap.Equals(IntPtr.Zero) Then
            m_address = Win32.MapViewOfFile(m_hFileMap, _
               Win32.FILE_MAP_WRITE, 0, 0, IntPtr.Zero)
        Else
            Throw New SerializationException("A SharedMemory object " & _
               "could not be deserialized.")
        End If
    End Sub
End Class

Class App
    <STAThread()> Shared Sub Main()
        Serialize()
        Console.WriteLine()
        Deserialize()
    End Sub

    Shared Sub Serialize()
        ' Create a hashtable of values that will eventually be serialized.
        Dim sm As New SharedMemory(1024, "MyMemory")
        Dim x As Int32
        For x = 0 To 99
            sm.SetByte(x, x)
        Next

        Dim b(9) As Byte
        For x = 0 To b.Length - 1
            b(x) = sm.GetByte(x)
        Next
        Console.WriteLine(BitConverter.ToString(b))

        ' To serialize the hashtable (and its key/value pairs), you must first 
        ' open a stream for writing. Use a file stream here.
        Dim fs As New FileStream("DataFile.dat", FileMode.Create)

        ' Construct a BinaryFormatter telling it where 
        ' the objects will be serialized to.
        Dim formatter As New BinaryFormatter(Nothing, _
           New StreamingContext(StreamingContextStates.CrossAppDomain))
        Try
            formatter.Serialize(fs, sm)
        Catch e As SerializationException
            Console.WriteLine("Failed to serialize. Reason: " + e.Message)
            Throw
        Finally
            fs.Close()
        End Try
    End Sub

    Shared Sub Deserialize()
        ' Declare the hashtable reference.
        Dim sm As SharedMemory = Nothing

        ' Open the file containing the data that you want to deserialize.
        Dim fs As New FileStream("DataFile.dat", FileMode.Open)
        Try
            Dim Formatter As New BinaryFormatter(Nothing, _
               New StreamingContext(StreamingContextStates.CrossAppDomain))

            ' Deserialize the SharedMemory object from the file and 
            ' assign the reference to the local variable.
            sm = DirectCast(Formatter.Deserialize(fs), SharedMemory)
        Catch e As SerializationException
            Console.WriteLine("Failed to deserialize. Reason: " & e.Message)
        Finally
            fs.Close()
        End Try

        ' To prove that the SharedMemory object deserialized correctly, 
        ' display some of its bytes to the console.
        Dim b(9) As Byte
        Dim x As Int32
        For x = 0 To b.Length - 1
            b(x) = sm.GetByte(x)
        Next
        Console.WriteLine(BitConverter.ToString(b))
    End Sub
End Class

// Note: You must compile this file using the C# /unsafe switch.
using System;
using System.IO;
using System.Collections;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.Runtime.InteropServices;
using System.Security.Permissions;

[assembly: SecurityPermission(
SecurityAction.RequestMinimum, Execution = true)]
// This class includes several Win32 interop definitions.
internal class Win32
{
    public static readonly IntPtr InvalidHandleValue = new IntPtr(-1);
    public const UInt32 FILE_MAP_WRITE = 2;
    public const UInt32 PAGE_READWRITE = 0x04;

    [DllImport("Kernel32")]
    public static extern IntPtr CreateFileMapping(IntPtr hFile,
        IntPtr pAttributes, UInt32 flProtect,
        UInt32 dwMaximumSizeHigh, UInt32 dwMaximumSizeLow, String pName);

    [DllImport("Kernel32")]
    public static extern IntPtr OpenFileMapping(UInt32 dwDesiredAccess,
        Boolean bInheritHandle, String name);

    [DllImport("Kernel32")]
    public static extern Boolean CloseHandle(IntPtr handle);

    [DllImport("Kernel32")]
    public static extern IntPtr MapViewOfFile(IntPtr hFileMappingObject,
        UInt32 dwDesiredAccess,
        UInt32 dwFileOffsetHigh, UInt32 dwFileOffsetLow,
        IntPtr dwNumberOfBytesToMap);

    [DllImport("Kernel32")]
    public static extern Boolean UnmapViewOfFile(IntPtr address);

    [DllImport("Kernel32")]
    public static extern Boolean DuplicateHandle(IntPtr hSourceProcessHandle,
        IntPtr hSourceHandle,
        IntPtr hTargetProcessHandle, ref IntPtr lpTargetHandle,
        UInt32 dwDesiredAccess, Boolean bInheritHandle, UInt32 dwOptions);
    public const UInt32 DUPLICATE_CLOSE_SOURCE = 0x00000001;
    public const UInt32 DUPLICATE_SAME_ACCESS = 0x00000002;

    [DllImport("Kernel32")]
    public static extern IntPtr GetCurrentProcess();
}


// This class wraps memory that can be simultaneously 
// shared by multiple AppDomains and Processes.
[Serializable]
public sealed class SharedMemory : ISerializable, IDisposable
{
    // The handle and string that identify 
    // the Windows file-mapping object.
    private IntPtr m_hFileMap = IntPtr.Zero;
    private String m_name;

    // The address of the memory-mapped file-mapping object.
    private IntPtr m_address;

    public unsafe Byte* Address
    {
        get { return (Byte*)m_address; }
    }

    // The constructors.
    public SharedMemory(Int32 size) : this(size, null) { }

    public SharedMemory(Int32 size, String name)
    {
        m_hFileMap = Win32.CreateFileMapping(Win32.InvalidHandleValue,
            IntPtr.Zero, Win32.PAGE_READWRITE,
            0, unchecked((UInt32)size), name);
        if (m_hFileMap == IntPtr.Zero)
            throw new Exception("Could not create memory-mapped file.");
        m_name = name;
        m_address = Win32.MapViewOfFile(m_hFileMap, Win32.FILE_MAP_WRITE,
            0, 0, IntPtr.Zero);
    }

    // The cleanup methods.
    public void Dispose()
    {
        GC.SuppressFinalize(this);
        Dispose(true);
    }

    private void Dispose(Boolean disposing)
    {
        Win32.UnmapViewOfFile(m_address);
        Win32.CloseHandle(m_hFileMap);
        m_address = IntPtr.Zero;
        m_hFileMap = IntPtr.Zero;
    }

    ~SharedMemory()
    {
        Dispose(false);
    }

    // Private helper methods.
    private static Boolean AllFlagsSet(Int32 flags, Int32 flagsToTest)
    {
        return (flags & flagsToTest) == flagsToTest;
    }

    private static Boolean AnyFlagsSet(Int32 flags, Int32 flagsToTest)
    {
        return (flags & flagsToTest) != 0;
    }


    // The security attribute demands that code that calls  
    // this method have permission to perform serialization.
    [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
    void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
    {
        // The context's State member indicates
        // where the object will be deserialized.

        // A SharedMemory object cannot be serialized 
        // to any of the following destinations.
        const StreamingContextStates InvalidDestinations =
                  StreamingContextStates.CrossMachine |
                  StreamingContextStates.File |
                  StreamingContextStates.Other |
                  StreamingContextStates.Persistence |
                  StreamingContextStates.Remoting;
        if (AnyFlagsSet((Int32)context.State, (Int32)InvalidDestinations))
            throw new SerializationException("The SharedMemory object " +
                "cannot be serialized to any of the following streaming contexts: " +
                InvalidDestinations);

        const StreamingContextStates DeserializableByHandle =
                  StreamingContextStates.Clone |
            // The same process.
                  StreamingContextStates.CrossAppDomain;
        if (AnyFlagsSet((Int32)context.State, (Int32)DeserializableByHandle))
            info.AddValue("hFileMap", m_hFileMap);

        const StreamingContextStates DeserializableByName =
            // The same computer.
                  StreamingContextStates.CrossProcess;
        if (AnyFlagsSet((Int32)context.State, (Int32)DeserializableByName))
        {
            if (m_name == null)
                throw new SerializationException("The SharedMemory object " +
                    "cannot be serialized CrossProcess because it was not constructed " +
                    "with a String name.");
            info.AddValue("name", m_name);
        }
    }


    // The security attribute demands that code that calls  
    // this method have permission to perform serialization.
    [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
    private SharedMemory(SerializationInfo info, StreamingContext context)
    {
        // The context's State member indicates 
        // where the object was serialized from.

        const StreamingContextStates InvalidSources =
                  StreamingContextStates.CrossMachine |
                  StreamingContextStates.File |
                  StreamingContextStates.Other |
                  StreamingContextStates.Persistence |
                  StreamingContextStates.Remoting;
        if (AnyFlagsSet((Int32)context.State, (Int32)InvalidSources))
            throw new SerializationException("The SharedMemory object " +
                "cannot be deserialized from any of the following stream contexts: " +
                InvalidSources);

        const StreamingContextStates SerializedByHandle =
                  StreamingContextStates.Clone |
            // The same process.
                  StreamingContextStates.CrossAppDomain;
        if (AnyFlagsSet((Int32)context.State, (Int32)SerializedByHandle))
        {
            try
            {
                Win32.DuplicateHandle(Win32.GetCurrentProcess(),
                    (IntPtr)info.GetValue("hFileMap", typeof(IntPtr)),
                    Win32.GetCurrentProcess(), ref m_hFileMap, 0, false,
                    Win32.DUPLICATE_SAME_ACCESS);
            }
            catch (SerializationException)
            {
                throw new SerializationException("A SharedMemory was not serialized " +
                    "using any of the following streaming contexts: " +
                    SerializedByHandle);
            }
        }

        const StreamingContextStates SerializedByName =
            // The same computer.
                  StreamingContextStates.CrossProcess;
        if (AnyFlagsSet((Int32)context.State, (Int32)SerializedByName))
        {
            try
            {
                m_name = info.GetString("name");
            }
            catch (SerializationException)
            {
                throw new SerializationException("A SharedMemory object was not " +
                    "serialized using any of the following streaming contexts: " +
                    SerializedByName);
            }
            m_hFileMap = Win32.OpenFileMapping(Win32.FILE_MAP_WRITE, false, m_name);
        }
        if (m_hFileMap != IntPtr.Zero)
        {
            m_address = Win32.MapViewOfFile(m_hFileMap, Win32.FILE_MAP_WRITE,
                0, 0, IntPtr.Zero);
        }
        else
        {
            throw new SerializationException("A SharedMemory object could not " +
                "be deserialized.");
        }
    }
}


class App
{
    [STAThread]
    static void Main(string[] args)
    {
        Serialize();
        Console.WriteLine();
        Deserialize();
    }

    unsafe static void Serialize()
    {
        // Create a hashtable of values that will eventually be serialized.
        SharedMemory sm = new SharedMemory(1024, "JeffMemory");
        for (Int32 x = 0; x < 100; x++)
            *(sm.Address + x) = (Byte)x;

        Byte[] b = new Byte[10];
        for (Int32 x = 0; x < b.Length; x++) b[x] = *(sm.Address + x);
        Console.WriteLine(BitConverter.ToString(b));

        // To serialize the SharedMemory object, 
        // you must first open a stream for writing. 
        // Use a file stream here.
        FileStream fs = new FileStream("DataFile.dat", FileMode.Create);

        // Construct a BinaryFormatter and tell it where 
        // the objects will be serialized to.
        BinaryFormatter formatter = new BinaryFormatter(null,
            new StreamingContext(StreamingContextStates.CrossAppDomain));
        try
        {
            formatter.Serialize(fs, sm);
        }
        catch (SerializationException e)
        {
            Console.WriteLine("Failed to serialize. Reason: " + e.Message);
            throw;
        }
        finally
        {
            fs.Close();
        }
    }


    unsafe static void Deserialize()
    {
        // Declare a SharedMemory reference.
        SharedMemory sm = null;

        // Open the file containing the data that you want to deserialize.
        FileStream fs = new FileStream("DataFile.dat", FileMode.Open);
        try
        {
            BinaryFormatter formatter = new BinaryFormatter(null,
                new StreamingContext(StreamingContextStates.CrossAppDomain));

            // Deserialize the SharedMemory object from the file and 
            // assign the reference to the local variable.
            sm = (SharedMemory)formatter.Deserialize(fs);
        }
        catch (SerializationException e)
        {
            Console.WriteLine("Failed to deserialize. Reason: " + e.Message);
            throw;
        }
        finally
        {
            fs.Close();
        }

        // To prove that the SharedMemory object deserialized correctly, 
        // display some of its bytes to the console.
        Byte[] b = new Byte[10];
        for (Int32 x = 0; x < b.Length; x++) b[x] = *(sm.Address + x);
        Console.WriteLine(BitConverter.ToString(b));
    }
}

平台

Windows 98、Windows 2000 SP4、Windows Millennium Edition、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

请参见

参考

System.Runtime.Serialization 命名空间
FlagsAttribute