"IF" code is not working inside for each? - vb.net

Question

so im learning to use socket and thread things in the networking software. so far, the software (which is not created by me) is able to chat in multiple group, but i'm tasked to allow user to code whisper feature. However, im stuck in the coding area, which im sure will work if the "if" function work inside "for each" function, anyhow here is my code mainly
Private clientCollection As New Hashtable()
Private usernameCollection As New Hashtable()
clientCollection.Add(clientID, CData)
usernameCollection.Add(clientID, username)
oh and before i forgot, the code above and below is on the server form page
on the client side, i write the code:
writer.write("PMG" & vbnewline & txtReceiverUsername & Message)
then next is the checking part on the server reading the message:
ElseIf message.Substring(0, 3) = "PMG" Then
'filter the message, check who to send to
Dim newMessage As String = message.Substring(3)
Dim messagearray As String() = newMessage.Split(vbNewLine)
Dim receiver As String = messagearray(1)
'0 = "", 1 = receiver, 2 = message
as i write before, clientcollection contain (clientID , connection data*) and usernamecollection contain (clientID, username). In my case, i only have the username data, and i need to trace it until the connection data on clientcollection hash table.
'find realid from usernamecollection, then loop clientcollection
Dim clientKey As String = 0
For Each de As DictionaryEntry In usernameCollection
'''''
'this if part Is Not working
If de.Value Is receiver Then
clientKey = de.Key
End If
'''''
Next de
'match objKey with clientcollection key
For Each dec As DictionaryEntry In clientCollection
If dec.Key = clientKey Then
Dim clients As ClientData = dec.Value
If clients.structSocket.Connected Then
clients.structWriter.Write("PMG" & messagearray(2))
End If
End If
Next dec
End If
so, how do i know that the if part is the wrong one? simply i tried these code before the "next de" code
For Each client As ClientData In clientCollection.Values
If client.structSocket.Connected Then
client.structWriter.Write("PMG" & "receiver:" & messagearray(1))
client.structWriter.Write("PMG" & "loop username: " & de.Value)
client.structWriter.Write("PMG" & "loop key: " & de.Key)
client.structWriter.Write("PMG" & "receiver key:" & clientKey)
End If
Next
the code allow me to check the de.key and de.value. they were correct, however the only thing that did not work is the code inside the "if" area.
Can anyone suggest other code maybe beside "if de.key = receiver"? I've also tried using the if de.key.equal(receiver) and it did not work too