C# 4 and .NET 4

User account Control ❘ 1405
An application manifest is an XML fi le similar to the application confi guration fi le. While the application
confi guration fi le has the fi le extension .config, the manifest ends with .manifest. The name of the
fi le mu s t b e s e t to t he n a m e of t he appl ic at ion , i nclud i ng t he . exe fi le extension followed by .manifest.
Visual Studio renames and copies the app.manifest fi le just as it does an application confi guration fi le.
The manifest fi le contains XML data, as shown here. The root element sembly> is a < , which contains the
child element rustInfo> t < . The administrator requirement is defi ned with the level attribute of the
< requestedExecutionLevel > e l e m e nt .
< xml version="1.0" encoding="utf - 8" >
< asmv1:assembly manifestVersion="1.0" xmlns="urn:schemas - microsoft - com:asm.v1"
xmlns:asmv1="urn:schemas - microsoft - com:asm.v1"
xmlns:asmv2="urn:schemas - microsoft - com:asm.v2"
xmlns:xsi="http://www.w3.org/2001/XMLSchema - instance" >
< assemblyIdentity version="1.0.0.0" name="MyApplication.app"/ >
< trustInfo xmlns="urn:schemas - microsoft - com:asm.v2" >
< security >
< requestedPrivileges xmlns="urn:schemas - microsoft - com:asm.v3" >
< requestedExecutionLevel level="requireAdministrator" uiAccess="false" / >
< /requestedPrivileges >
< /security >
< /trustInfo >
< /asmv1:assembly >
code snippet AdminRightsRequired/app.manifest
When starting the application this way, you get an elevation prompt where the user is asked if he or she trusts
the application to run with administrative privileges.
With the requestedExecutionLevel setting, you can specify the values requireAdministrator ,
highestAvailable , and asInvoker . The value highestAvailable means that the application gets the
privileges the user has — but only after getting the consent from the user. The value requireAdministrator
requires Administrator privileges. If the user is not logged on to the system as Administrator, a login dialog
appears where the user can log in as Administrator for the application. The value asInvoker means that the
application is running with the security token of the user.
The uiAccess attribute specifi es if the application requires input to a higher - privilege - level window on the
desktop. For example, an onscreen keyboard needs to drive input to other windows on the desktop, so
the setting should be set to true for the application to display the onscreen keyboard. Non - UI - accessible
applications should have this attribute set to false .
Another way to get admin privileges to an application is to write a Windows service.
Because UAC applies to interactive processes only, a Windows service can get admin
privileges. You can also write an unprivileged Windows application to communicate
with the privileged Windows service by using WCF or another communication
technology.
Windows services are covered in Chapter 25, “Windows Services.” WCF is covered in
Chapter 43, “Windows Communication Foundation.”
shield icon
If an application or a task from an application requires administrative privileges, the user is informed by an
easily recognizable shield icon. The shield icon is attached to the controls that require elevation. The user
expects to see an elevation prompt when clicking on an item with a shield. Figures A - 5 and A - 6 show the
shield in use. The Task Manager requires elevation to see processes from all users. Within User Accounts,
adding or removing user accounts requires elevation as well as setting up parental controls.
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