Struggling with OrderBy Lambda expression

I'm getting my feet wet with Lambda expressions and it's rather overwhelming.

I have a UserPrincipal object called SelectedUser. I wish to get a sorted list of the user's groups

This is what I have so far but when I include that code my application's form flashes a few times and closes! Also, what is the significance of the "r" in the "Return From r" statement?

Code:

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Dim SortedGroups As PrincipalSearchResult(Of Principal) = GetSortedGroups(Me.SelectedUser.GetGroups())

    Private Function GetSortedGroups(ByVal psp As PrincipalSearchResult(Of Principal)) As PrincipalSearchResult(Of Principal)
        Return From r In psp.OrderBy(Function(t) t.Name)
    End Function

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Right, after some trial and error it's working. I had to cast it to an array

Code:

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    Private Function GetSortedGroups(ByVal psp As PrincipalSearchResult(Of Principal)) As Principal()
        Return (From r In psp.OrderBy(Function(grp) grp.Name)).ToArray()
    End Function

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Would someone mind explaining why this is so?

Quote:

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Originally Posted by Ginolard

Right, after some trial and error it's working. I had to cast it to an array

Code:

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    Private Function GetSortedGroups(ByVal psp As PrincipalSearchResult(Of Principal)) As Principal()
        Return (From r In psp.OrderBy(Function(grp) grp.Name)).ToArray()
    End Function

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Would someone mind explaining why this is so?

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You need to cast it as an Array because your return type Principal() is an array.

No, I meant why does the function have to return an array? Originally I was trying to return a PrincipalSearchResult collection which, obviously, wasn't working.

LinQ is confusing :(

Quote:

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Originally Posted by Ginolard

No, I meant why does the function have to return an array? Originally I was trying to return a PrincipalSearchResult collection which, obviously, wasn't working.

LinQ is confusing :(

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Did you try .ToList
In regards to confusing, only when you do not take time to learn it rather then simply using LINQ.