IPermission.Union(IPermission) Method

Definition

Namespace:

System.Security

Assembly:

System.Runtime.dll

Creates a permission that is the union of the current permission and the specified permission.

public:
 System::Security::IPermission ^ Union(System::Security::IPermission ^ target);

public System.Security.IPermission? Union (System.Security.IPermission? target);

abstract member Union : System.Security.IPermission -> System.Security.IPermission

Public Function Union (target As IPermission) As IPermission

Parameters

target

IPermission

A permission to combine with the current permission. It must be of the same type as the current permission.

Returns

IPermission

A new permission that represents the union of the current permission and the specified permission.

Exceptions

ArgumentException

The target parameter is not null and is not of the same type as the current permission.

Examples

The following code example demonstrates implementing the Union method. This code example is part of a larger example provided for the IPermission class.

    // Return a new object that contains the union of 'this' and 'target'.
    // Note: You do not have to implement this method. 
    // If you do not, the version
    // in CodeAccessPermission does this:
    //    1. If target is not null, a NotSupportedException is thrown.
    //    2. If target is null, then Copy is called and 
    //       the new object is returned.
public:
    virtual IPermission^ Union(IPermission^ target) override
    {
        // If 'target' is null, then return a copy of 'this'.
        if (target == nullptr)
        {
            return Copy();
        }

        // Both objects must be the same type.
        SoundPermission^ soundPerm = VerifyTypeMatch(target);

        // If 'this' or 'target' are unrestricted, 
        // return a new unrestricted permission.
        if (specifiedAsUnrestricted || soundPerm->specifiedAsUnrestricted)
        {
            return Clone(true, SoundPermissionState::PlayAnySound);
        }

        // Return a new object with the calculated, unioned permission value.
        return Clone(false, (SoundPermissionState)
            Math::Max((int) stateFlags, (int) soundPerm->stateFlags));
    }

// Return a new object that contains the union of 'this' and 'target'.
// Note: You do not have to implement this method. If you do not, the version
// in CodeAccessPermission does this:
//    1. If target is not null, a NotSupportedException is thrown.
//    2. If target is null, then Copy is called and the new object is returned.
public override IPermission Union(IPermission target)
{
    // If 'target' is null, then return a copy of 'this'.
    if (target == null) return Copy();

    // Both objects must be the same type.
    SoundPermission soundPerm = VerifyTypeMatch(target);

    // If 'this' or 'target' are unrestricted, return a new unrestricted permission.
    if (m_specifiedAsUnrestricted || soundPerm.m_specifiedAsUnrestricted)
        return Clone(true, SoundPermissionState.PlayAnySound);

    // Return a new object with the calculated, unioned permission value.
    return Clone(false, (SoundPermissionState)
        Math.Max((Int32)m_flags, (Int32)soundPerm.m_flags));
}

' Return a new object that contains the union of 'this' and 'target'.
' Note: You do not have to implement this method. If you do not, the version
' in CodeAccessPermission does this:
'    1. If target is not null, a NotSupportedException is thrown.
'    2. If target is null, then Copy is called and the new object is returned.
Public Overrides Function Union(ByVal target As IPermission) As IPermission
    ' If 'target' is null, then return a copy of 'this'.
    If target Is Nothing Then
        Return Copy()
    End If
    ' Both objects must be the same type.
    Dim soundPerm As SoundPermission = VerifyTypeMatch(target)

    ' If 'this' or 'target' are unrestricted, return a new unrestricted permission.
    If m_specifiedAsUnrestricted OrElse soundPerm.m_specifiedAsUnrestricted Then
        Return Clone(True, SoundPermissionState.PlayAnySound)
    End If
    ' Return a new object with the calculated, unioned permission value.
    Return Clone(False, CType(Math.Max(CType(m_flags, Int32), CType(soundPerm.m_flags, Int32)), SoundPermissionState))

End Function 'Union

Remarks

The result of a call to Union is a permission that represents all the operations represented by both the current permission and the specified permission. Any demand that passes either permission passes their union.

The following statements are required to be true for all implementations of the Union method. X and Y represent IPermission objects that are not null.

• X.Union(X) returns an object that has the same value as X.

• X.Union(Y) returns an object that has the same value as the object returned by Y.Union(X).

• X.Union(null) returns an object that has the same value as X.