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An element with same key but a different value already exist

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Posted on by Ahsan baig 123

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I am using power shell to integrate data verse table to business central. However when i execute the script i am facing this issue

System.ArgumentException: An element with the same key but a different value already exists. Key: 'systemuser'

Please let me know how this issue can be resolved.

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Dynamics 365 Business Central

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YUN ZHU 103,089 Super User 2026 Season 2 on at

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Hi, I didn't encounter this problem when testing before. You can check the difference with your code.

https://yzhums.com/17065/

Thanks.

ZHU
CU19091850-0 6 on at

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I have added new field in Customer Asset table, and trying to run the Powershell script. However, I am also getting similar error:

Please suggest how o resolve this issue.
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Rishabh Kanaskar 6,231 Super User 2026 Season 1 on at

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This error is pretty common when working with PowerShell + Dataverse + Business Central APIs. It usually happens because of how you’re building your hashtable/dictionary for headers, query parameters, or JSON payload before calling the API.

1. The error:

> System.ArgumentException: An element with the same key but a different value already exists. Key: 'systemuser'

means that somewhere in your code you are adding the same key twice to a collection that enforces uniqueness, such as:

> A PowerShell Hashtable (@{})

> A Dictionary object in .NET

> Or a header collection in Invoke-RestMethod or Invoke-WebRequest

If you accidentally do something like this:

$headers = @{
"Authorization" = "Bearer $token"
"Content-Type" = "application/json"
"systemuser" = "value1"
"systemuser" = "value2" # <-- same key, different value
}

> PowerShell will throw the exact error you’re seeing.

2. Fix in PowerShell

If you are using a Hashtable, you can check for existing keys before adding:

if (-not $headers.ContainsKey("systemuser")) {
$headers["systemuser"] = "yourvalue"
} else {
# Optionally overwrite instead of adding again
$headers["systemuser"] = "yourvalue"
}

> Or simply remove the duplicate definition.

Thanks

Rishabh