Deserialize PSObject from JSON to a list in C#

Question

I have an application in C# to display information from Active Directory using PowerShell.

class userps { public string Name { get; set; } public bool Enabled { get; set; } } PSObject[] results = pipeline.Invoke().ToArray(); List<userps> listUserps = new List<userps>(); foreach (PSObject obj in results) { lista = JsonConvert.DeserializeObject<List<userps>>(obj.ToString()); }

If the object returns data of at least two elements, for example:

[ { "Name":"xxx", "Enabled":true }, { "Name":"yyy", "Enabled":true } ]

Then everything is fine, List.Count = 2. If, however, it returns one element:

[ { "Name":"xxx", "Enabled":true } ]

Then List.Count = 0 and there is an exception:

Newtonsoft.Json.JsonSerializationException: „Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[ConsoleApp1.userps]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.
To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object.
JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.
Path 'Name', line 2, position 11.”

How do I solve this problem so it would work for one element and also for several?

Possible duplicate of JsonConvert.DeserializeObject<IEnumerable<Book>> — SᴇM
– SᴇM, Commented Jun 11, 2018 at 10:14
Also: Possible duplicate of Cannot deserialize the JSON array (e.g. 1,2,3) into type ' ' because type requires JSON object (e.g. {“name”:“value”}) to deserialize correctly — SᴇM
– SᴇM, Commented Jun 11, 2018 at 10:17
@SeM your duplicated links are not related to this case. OP already knows and has a success when deserailizing an array. He only fails when the array contains one element — CodeNotFound
– CodeNotFound, Commented Jun 11, 2018 at 10:20
@CodeNotFound I just want to show OP that if he have correct json string and deserialized it correctly, it is unlikely to happen, cause it doesn't matter if there 1 element or 2. — SᴇM
– SᴇM, Commented Jun 11, 2018 at 11:35

Peter Mortensen · Accepted Answer · 2019-08-09 10:05:16Z

It looks like the object you get from your PowerShell command is not a collection and is serialized as an object in JSON. It's the common behaviour of PowerShell when a command returns only one object instead of a list.

Example:

Get-Service | ConvertTo-Json [ { "Name": "AdobeFlashPlayerUpdateSvc", ... }, { "Name": "ALG", ... }, ... ] Get-Service -Name 'NetLogon' | ConvertTo-Json { "Name": "NetLogon", ... }

To avoid this, encapsulate your command in an array constructor and replace the pipe by the InputObject parameter:

ConvertTo-Json -InputObject @(Get-Service -Name 'NetLogon') [ { "Name": "NetLogon", ... } ]

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