FileDialogPermission.Union 方法

创建一个权限，该权限是当前权限与指定权限的并集。

**命名空间:**System.Security.Permissions
**程序集:**mscorlib（在 mscorlib.dll 中）

语法

声明
Public Overrides Function Union ( _
    target As IPermission _
) As IPermission
用法
Dim instance As FileDialogPermission
Dim target As IPermission
Dim returnValue As IPermission

returnValue = instance.Union(target)

public override IPermission Union (
    IPermission target
)

public:
virtual IPermission^ Union (
    IPermission^ target
) override

public IPermission Union (
    IPermission target
)

public override function Union (
    target : IPermission
) : IPermission

参数

• target
  将与当前权限合并的权限。它必须与当前权限属于同一类型。

返回值

一个新权限，它表示当前权限与指定权限的并集。

异常

异常类型	条件
ArgumentException	target 参数不是 空引用（在 Visual Basic 中为 Nothing），而且与当前权限不是同一类型。

备注

调用 Union 得到一个权限，该权限表示由当前权限和指定权限表示的所有操作。通过任何一个权限的任何请求都会通过这些权限的并集。

示例

下面的代码示例旨在演示 Union 方法的行为，而不演示其用法。一般情况下，权限类的方法由安全性基础结构使用，而不在应用程序中使用。但是，下面的代码示例将演示在从您的代码执行该方法时，该方法将如何执行。有关完整的代码示例，请参见 FileDialogPermission 类。

Private Function UnionDemo() As Boolean 
    Dim returnValue As Boolean = True
    
    fileDialogPerm3 = CType(fileDialogPerm1.Union(fileDialogPerm2), FileDialogPermission)
    
    If fileDialogPerm3 Is Nothing Then
        Console.WriteLine("The union of " + fileDialogPerm1.Access.ToString() + _
        " and " + fileDialogPerm2.Access.ToString() + " is null.")
    Else
        Console.WriteLine("The union of " + fileDialogPerm1.Access.ToString() + _
        " and " + fileDialogPerm2.Access.ToString() + " = " + _
        CType(fileDialogPerm3, FileDialogPermission).Access.ToString())
    End If
    
    Return returnValue

End Function 'UnionDemo
 

private bool UnionDemo()
{
    bool returnValue = true;

            fileDialogPerm3 = (FileDialogPermission)fileDialogPerm1.Union(fileDialogPerm2);

            if (fileDialogPerm3 == null)
            {
                Console.WriteLine("The union of " + fileDialogPerm1.Access + 
                    " and " + fileDialogPerm2.Access + " is null.");
            }
            else
            {
                Console.WriteLine("The union of " + fileDialogPerm1.Access + " and " +
                    fileDialogPerm2.Access + " = " +
                    ((FileDialogPermission)fileDialogPerm3).Access.ToString());
            }

    return returnValue;

}

bool UnionDemo()
{
    bool returnValue = true;
    FileDialogPermission^ fileDialogIdPerm1 = gcnew FileDialogPermission(FileDialogPermissionAccess::Open );
    FileDialogPermission^ fileDialogIdPerm2 = gcnew FileDialogPermission( FileDialogPermissionAccess::OpenSave );
    FileDialogPermission^ fileDialogIdPerm3 = gcnew FileDialogPermission(PermissionState::None);
    fileDialogIdPerm3 = dynamic_cast<FileDialogPermission^>(fileDialogIdPerm1->Union( fileDialogIdPerm2 ));
    if ( fileDialogIdPerm3 == nullptr )
    {
        Console::WriteLine( "The union of {0} and {1} is null.", 
            fileDialogIdPerm1->Access, fileDialogIdPerm2->Access );
    }
    else
    {
        Console::WriteLine( "The union of {0} and {1} = {2}", 
            fileDialogIdPerm1->Access, fileDialogIdPerm2->Access, (dynamic_cast<FileDialogPermission^>(fileDialogIdPerm3))->Access );
    }
    return returnValue;
}

// Union creates a new permission that is the union of 
// the current permission and the
// specified permission.
private boolean UnionDemo() 
{
    boolean returnValue = true;
    FileDialogPermissionAccess fileDialog1[] = 
        new FileDialogPermissionAccess[1];
    FileDialogPermissionAccess fileDialog2[] = 
        new FileDialogPermissionAccess[1];
    FileDialogPermission fileDialogIdPerm1[] = 
        new FileDialogPermission[1];
    FileDialogPermission fileDialogIdPerm2[] = 
        new FileDialogPermission[1];
    IPermission fileDialogIdPerm3;
    FileDialogGenerator fileDialogGen1 =  
        new FileDialogGenerator();
    FileDialogGenerator fileDialogGen2 =  
        new FileDialogGenerator();
    fileDialogGen1.ResetIndex();
    while(fileDialogGen1.CreateFileDialog(fileDialogIdPerm1, 
        fileDialog1)) {
        if (fileDialogIdPerm1[0] == null) {
            continue ;
        }
        Console.WriteLine("************************" 
            + "**********************************\n");
        fileDialogGen2.ResetIndex();
        
        while(fileDialogGen2.CreateFileDialog(fileDialogIdPerm2, 
            fileDialog2)) {
            if (fileDialogIdPerm2[0] == null) {
                continue ;
            }
            fileDialogIdPerm3 =((FileDialogPermission)(
                fileDialogIdPerm1[0].Union(fileDialogIdPerm2[0])));
            fileDialogIdPerm3 = fileDialogIdPerm1[0].
                Union(fileDialogIdPerm2[0]);
            
            if (fileDialogIdPerm3 == null) {
                Console.WriteLine(("The union of " + fileDialog1[0] 
                    + " and " + fileDialog2[0] + " is null."));
            }
            else {
                Console.WriteLine(("The union of " 
                    + fileDialogIdPerm1[0].get_Access() + " and " 
                    + fileDialogIdPerm2[0].get_Access() + " = " 
                    + ((FileDialogPermission)(fileDialogIdPerm3)).
                    get_Access().ToString()));
            }
        }
    }
    return returnValue ;
} //UnionDemo

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

FileDialogPermission 类
FileDialogPermission 成员
System.Security.Permissions 命名空间