Hi,
My main form's only TreeView displays added icon entries fine, but when I come to clear it for a fresh set of icon additions, I get an error "key already used"   when I code:-

where key - which should be cleared - and key3 have the same value.  

Am I doing something wrong?  Can I clear the keys without having to loop through all the entries (potentially hundreds), deleting them?!

Thanks,
C.

Your snippet of code does not make much sense or explain what is going on with your variables key, key2 and key3. (what is their value?)

Nothing will happen to your key key2 key3 variables they will be whatever you set them to.

this code..
gives no errors

TreeView.Clear DOES clear the keys

The keys are stored in TreeView1.Keys
 the Key you provide in TreeView1.Add(Key, Text, Pic) gives the TreeView item an identifier
Eg.

You understand by "Key" it means a unique name ,nothing to do with keyboard yes?

the code…
TreeView1.Add(Key2, "Key2")
means Key2 must be a string variable holding a key name like Dim Key2 As String = "Keyname2"

post more complete code so we can see the errors better and not try to guess

Just a note:

To make a variable (that's not an object) have its value changed in a function parameter the ByRef keyword must be used on both sides of the command.
eg..
110

if you do not see the ByRef then a non object datatype will never be affected.

object datatypes and arrays work different as they are already pointers.

for example the following works fine without ByRef
110
120
130

Hope that makes sense ,, and helps

Thanks for the reassuring info Bruce,
…This 'error' case was my inattentive debugging, and garbage-In > garbage-Out data (a badly constructed .json input file :roll: )
so I was adding clashing keys AFTER my treeView.clear !

The byRef usage is new to me, so an additional way of changing values beyond a function's Return expression  

Thanks again.
C.