RESTMan | IDEA插件之REST风格接口调试工具，支持json、xml报文，语法高亮和语法检查 | Plugin library

Try unicode encoding:

Your user parameter in the request is an array of jsons, so you'd need to specify the index to access individual names

It would appear that you have two layers of JSON encoding: One done already by your tools (ASP.NET and Invoke-RestMethod in PowerShell), and one done by yourself manually.

Server side:

1. You have an object containing a key result with value ok.
2. You call JsonSerializer.Serialize on that object, turning it into a string (a JSON string representing the object): {"result":"ok"}
3. You return this string from your request handler method.
4. ASP.NET takes your value and serializes it to JSON (again!), turning it into another string (a JSON string representing another JSON string representing the object): "{\"result\":\"ok\"}"
5. This double-encoded data is sent over the wire and returned in the HTTP request.

Client side:

1. PowerShell receives the raw string "{\"result\":\"ok\"}" from your server.
2. Since the content type is application/json, the Invoke-RestMethod function deserializes it for you, resulting in a new string value {"result":"ok"}, which is the original data returned from your request handler (a JSON string representing your object)
3. You call ConvertFrom-Json on that string, deserializing it a second time, resulting in an object containing a key result and value ok.

You see, if you'd just neither manually serialize nor manually deserialize your data but instead simply return an object and treat $returnData as object too (since your tools on both ends of the wire already take care of that for you anyway), you would end up with the same result, but you'd get the expected once-encoded JSON string over the wire instead of the twice-encoded one you see now.