Error This key is already associated with an element of this collection

calendar_today Asked Feb 5, 2014
thumb_up 12 upvotes
history Updated April 14, 2026

Direct Answer

Adding keys with dictionaries is only possible when a key does not already exist. Accidentally you could entered the key before, or you are watching the key with the debug…. This is a prose walkthrough, ranked #144th of 303 by community upvote score, from 2014.


The Problem (Q-score 5, ranked #144th of 303 in the Excel VBA archive)

The scenario as originally posted in 2014

I am working on vba macros. I was trying to use a dictionary. But it is giving error 457 with debugger pointing to toprow.Add ActiveCell.value, val. Can anyone please tell the issue? I even used Cstr(activecell.value), Cstr(val) as mentioned in one of the answer on similar issue.

Dim toprow As New Dictionary, Dictkey As Variant
Dim val As String

Range("A1").Activate 
i = 0
Do Until i = ColLen
    val = Chr(65 + i)
    toprow.Add ActiveCell.value, val
    i = i + 1
    ActiveCell.Offset(0, 1).Activate
Loop

Why community consensus is tight on this one

Across 303 Excel VBA entries in the archive, the accepted answer here holds solid answer (above median) status — meaning voters are unusually aligned on the right fix.


The Verified Solution — solid answer (above median) (+12)

Verbal answer — walkthrough without a code block

Note: the verified answer is a prose walkthrough. If you need a runnable sample, check Excel VBA entries ranked in the top 10 of the same archive.

Adding keys with dictionaries is only possible when a key does not already exist. Accidentally you could entered the key before, or you are watching the key with the debug watcher, creating the key instanteneously. (= If you watch a certain key in a dictionary it gets created if it doesn’t already exist).

You have to

  • make sure you are not watching the key with the debugger
  • create unique entries by testing on d.Exists(keyname) and then use the d.Add keyname, value method
  • alternatively you can default to overwrite existing keys by using d.Item(keyname) = value


When to Use It — classic (2013–2016)

Ranked #144th in its category — specialized fit

This pattern sits in the 96% tail relative to the top answer. Reach for it when your scenario closely matches the question title; otherwise browse the Excel VBA archive for a higher-consensus alternative.

What changed between 2014 and 2026

The answer is 12 years old. The Excel VBA object model has been stable across Office 2013, 2016, 2019, 2021, 365, and 2024/2026 LTSC, so the pattern still compiles. Changes that might affect you: 64-bit API declarations (use PtrSafe), blocked macros in downloaded files (Mark-of-the-Web), and the shift toward Office Scripts for web-first workflows.

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Frequently Asked Questions

Is this above-median answer still worth copying?
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Answer score +12 vs the Excel VBA archive median ~4; this entry is solid. The score plus 5 supporting upvotes on the question itself (+5) means the asker and 11 subsequent voters all validated the approach.

The answer has no code block — how do I turn it into a snippet?
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Use the walkthrough above as a checklist, then open a top-10 Excel VBA archive entry for a concrete starting template you can adapt.

Published around 2014 — what’s changed since?
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Published 2014, which is 12 year(s) before today’s Office 2026 build. The Excel VBA object model has had no breaking changes in that window. Three things to re-test: (1) blocked macros on downloaded files (Mark-of-the-Web), (2) 64-bit API declarations (PtrSafe, LongPtr), (3) any shift toward Office Scripts for web scenarios.

Which Excel VBA pattern ranks just above this one at #143?
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The pattern one rank above is “Excel: Formulas for converting data among column / row / matrix”. If your use case overlaps, compare both before committing.

Data source: Community-verified Q&A snapshot. Q-score 5, Answer-score 12, original post 2014, ranked #144th of 303 in the Excel VBA archive. Last regenerated April 14, 2026.

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