For Each loop on an array of List(Of KeyValuePair(Of String, Integer))

Question

I'm having problems doing a For Each loop on a "List(Of KeyValuePair(Of" collection.

I'm passing a ParamArray to a Function

ParamArray args() As List(Of KeyValuePair(Of String, Integer))

I'm then trying to do a For Each on the Collection

For Each arg As KeyValuePair(Of String, Integer) In args

The error I'm getting is:

Value of type 'System.Collections.Generic.List(Of System.Collections.Generic.KeyValuePair(Of String, Integer))' cannot be converted to 'System.Collections.Generic.KeyValuePair(Of String, Integer)'

I just can't figure out how to do this, and I can't find any examples of how to do this.

My only thought right now is to do

For Each arg As Object In args

Then converting the object to a KeyValuePair, but there must be a neater way of doing this...

As was pointed out args is declared as an array. If that isn't your intention, removing the `()`'s should fix it. — tinstaafl, Sep 04 '14 at 15:22

Brandon · Accepted Answer · 2014-09-04T15:25:12.503

5

args is an array. That means that you have an array of List(Of KeyValuePair(Of String, Integer)).

To access each item in a for each you will need to do this (untested):

For Each arg As List(Of KeyValuePair(Of String, Integer)) In args
    For Each kvp as KeyValuePair(Of String, Integer) In arg
    ' Do Stuff
    Next
Next

As per my comment above: you'd probably be better off using a Dictionary(Of String, Integer) and some Linq statements.

Edit: Also, depending on what you're trying to do with each item, modifying the item in any way will result in an exception because you can't modify a collection you're iterating over.

edited Sep 04 '14 at 15:25

answered Sep 04 '14 at 15:15

Brandon

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Thanks for that, this option worked fine. This ParamArray is for a flexible number of Parameters. The original code (VB6) used Optional and isMissing, which I can't do in VB.NET, this was my solution. – JA12 Sep 04 '14 at 15:47
1

Glad my solution worked. Would you mind marking the question as answered for future reference? – Brandon Sep 04 '14 at 15:48
1

Click the checkmark beside my answer. It will turn green which will mark the question as answered. – Brandon Sep 04 '14 at 15:54
1

OK, that wasn't obvious. I was looking at the top for something relating to the original question... – JA12 Sep 05 '14 at 08:15

score 1 · Answer 2 · answered Sep 04 '14 at 15:32

This declares an array of lists:

ParamArray args() As List(Of KeyValuePair(Of String, Integer))

You probably meant an array of KVP (option #1):

ParamArray args As KeyValuePair(Of String, Integer)

Or (option #2):

args() As KeyValuePair(Of String, Integer)

Or (option #3):

args As List(Of KeyValuePair(Of String, Integer))

For Each loop on an array of List(Of KeyValuePair(Of String, Integer))

2 Answers2