Cómo forzar que una aplicación WPF se ejecute en modo Administrador

Si no quieres romper el Clickonce este código es la mejor solución:

using System.Security.Principal;
using System.Management;
using System.Diagnostics;
using System.Reflection;
//Put this code in the main entry point for the application
// Check if user is NOT admin 
if (!IsRunningAsAdministrator())
{
    // Setting up start info of the new process of the same application
    ProcessStartInfo processStartInfo = new ProcessStartInfo(Assembly.GetEntryAssembly().CodeBase);

    // Using operating shell and setting the ProcessStartInfo.Verb to “runas” will let it run as admin
    processStartInfo.UseShellExecute = true;
    processStartInfo.Verb = "runas";

    // Start the application as new process
    Process.Start(processStartInfo);

    // Shut down the current (old) process
    System.Windows.Forms.Application.Exit();
    }
}

/// <summary>
/// Function that check's if current user is in Aministrator role
/// </summary>
/// <returns></returns>
public static bool IsRunningAsAdministrator()
{
    // Get current Windows user
    WindowsIdentity windowsIdentity = WindowsIdentity.GetCurrent();

    // Get current Windows user principal
    WindowsPrincipal windowsPrincipal = new WindowsPrincipal(windowsIdentity);

    // Return TRUE if user is in role "Administrator"
    return windowsPrincipal.IsInRole(WindowsBuiltInRole.Administrator);
}

Fundada en: http://matijabozicevic.com/blog/wpf-winforms-development/running-a-clickonce-application-as-administrator-also-for-windows-8