When should I use LINQ for C#? [closed]

I find that I’m using LINQ just about any time that I would have previously written a loop to fill a container. I use LINQ to SQL as my ORM and lots of LINQ everywhere else.

Here’s a little snippet that I wrote for an Active Directory helper class that finds out if a particular user is an a particular group. Note the use of the Any() method to iterate over the user’s authorization groups until it finds one with a matching SID. Much cleaner code than the alternative.

private bool IsInGroup( GroupPrincipal group, UserPrincipal user )
{
    if (group == null || group.Sid == null)
    {
        return false;
    }
    return user.GetAuthorizationGroups()
               .Any( g => g.Sid != null && g.Sid.CompareTo( group.Sid ) == 0 );
}

Alternative:

private bool IsInGroup( GroupPrincipal group, UserPrincipal user )
{
    if (group == null || group.Sid == null)
    {
        return false;
    }
    bool inGroup = false;
    foreach (var g in user.GetAuthorizationGroups())
    {
         if ( g => g.Sid != null && g.Sid.CompareTo( group.Sid ) == 0 )
         {
            inGroup = true;
            break;
         }
    }
    return inGroup;
}

or

private bool IsInGroup( GroupPrincipal group, UserPrincipal user )
{
    if (group == null || group.Sid == null)
    {
        return false;
    }

    foreach (var g in user.GetAuthorizationGroups())
    {
         if ( g => g.Sid != null && g.Sid.CompareTo( group.Sid ) == 0 )
         {
            return true;
         }
    }
    return false;
}

Here’s a snippet that does a search against a repository, orders, and converts the first 10 matching business objects into a view-specific model (Distance is the Levenshtein edit distance of the matching model’s unique id from the uniqueID parameter).

model.Results = this.Repository.FindGuestByUniqueID( uniqueID, withExpired )
                               .OrderBy( g => g.Distance )
                               .Take( 10 )
                               .ToList()
                               .Select( g => new GuestGridModel( g ) );