VB.net Trim function - string

Question

I have an issue with trim the string method NOT working completely I have reviewed MS Docs and looked of forums but with no luck... It's probably something simple or some other parameter is missing. This is just a sample,
Please note I need to pick up text before and after #, hence than I was planning to use # as a separator. Trim start # #, Trim End # #. I can't use The last Index or Replace per my understanding they have no direction. But perhaps I am misunderstood MS docs regards to trim Start and End as well...
thanks!
Dim str As String = "this is a #string"
Dim ext As String = str.TrimEnd("#")
MsgBox(ext)
ANSWER:
I found a solution for my problem, if you experience similar please see below:
1st: Trim end will NOT scan for the "character" from the Right as I originally thought it will just remove it from the right.... A weak function I would say:). IndexOf direction ID would be a very simple and helpful. Regards My answer was answered by Andrew, thanks!
Now there is another way around it if you try to split a SINGLE String INTO - QTY based on CHARACTER separation and populate fields accordingly.
Answer is ArrayList. Array List will ID each String so you can avoid repeated populations and etc. After you can use CASE or IF to populate accordingly.
Dim arrList As New ArrayList("this is a # string".Split("#"c)) ' Will build the list of your strings
Dim index As Integer = 1 ' this will help us index the strings 1st, 2nd and etc.
For Each part In arrList 'here we are going thru the list
Select Case index ' Here we are identifying which field we are populating
Case 1 '1st string(split)
MsgBox("1 " & arrList(0) & index) '1st string value left to SPLIT arrList(0).
Case 2 '2nd string(split)
MsgBox("2 " & arrList(1) & index) '2nd string value left to SPLIT arrList(1).
End Select
index += 1 'Here we adding one shift thru strings as we go
Next

Answer 1

Rather than:
Dim str As String = "this is a #string"
Dim ext As String = str.TrimEnd("#")
Try:
Dim str As String = "this is a #string"
Dim ext As String = str.Replace("#", "")

Answer 2

Dim str As String = "this is a #string"
Dim parts = str.Split("#"c)
For Each part in parts
Console.WriteLine($"|{part}|")
Next
Output:
|this is a |
|string|

Answer 3

Maybe there is a better way as we know there are multiple things to do the same thing.
The solution I used is below:
Dim arrList As New ArrayList("this is a # string".Split("#"c)) ' Will build the list of your strings
Dim index As Integer = 1 ' this will help us index the strings 1st, 2nd and etc.
For Each part In arrList 'here we are going thru the list
Select Case index ' Here we are identifying which field we are populating
Case 1 '1st string(split)
MsgBox("1 " & arrList(0) & index) '1st string value left to SPLIT arrList(0).
Case 2 '2nd string(split)
MsgBox("2 " & arrList(1) & index) '2nd string value left to SPLIT arrList(1).
End Select
index += 1 'Here we adding one shift thru strings as we go
Next