Run code with elevated privileges in SharePoint

A task that is pretty common is to make some code that requires resources in sharepoint that the logged in user does not always have access to.

My latest web part warns users when their account or password is close to expiration (we have sharepoint users that do not log on to any computer using their account, so they will never get a warning otherwise).
This web part uses a list in the root web that keeps track of when a warning email was last sent to the user.
This list could not consistently be read since a few accounts does not have access to the rootweb.

I have also had to use this when writing to a websites property bag. Only owners were able to do that,
in a custom web part of mine.

There are 2 ways to do it.

1: Elevated Priviledges

protected void Button1_Click(object sender, EventArgs e)
{
   SPSecurity.CodeToRunElevated elevatedGetSitesAndGroups = new SPSecurity.CodeToRunElevated(GetSitesAndGroups);
   SPSecurity.RunWithElevatedPrivileges(elevatedGetSitesAndGroups);
}

GetSitesAndGroups is the method to run.
This method requires you to use methods that have no return type and no parameters.

This can also be done with anonymous methods like this:

SPSecurity.RunWithElevatedPrivileges(delegate()
{
    // implementation details omitted
});

Anonymous methods is not really something I ever use, so I haven’t quite figured them out yet.
I could not put this inside my method, and have return statements inside the block.

To make this work you have to create a new SPSite object, otherwise it will continue to use the SPSite where the current logged in users permissions are located.

SPSecurity.RunWithElevatedPrivileges(delegate()
{
    using (SPSite site = new SPSite(web.Site.ID))
    {
    // implementation details omitted
    }
});

More details here

2: System Account User Token
I found an even better solution online though, from Daniel Larsson

He states that he has a better way of getting things done, and suggest we do not use the SPSecurity method unless we need to use network resources.

His solution is simple, he created a new site with the system account as user token.

SPUserToken sysToken = SPContext.Current.Site.SystemAccount.UserToken;
using(var systemSite = new SPSite(SPContext.Current.Site.ID, sysToken))
{
    using (var sysWeb = systemSite.OpenWeb(SPContext.Current.Web.ID))
    {
        // Perform elevated actions here
    }
}