Working with restricted string field values in .NET Core WebAPI 3.1

I’m working on a webapi project using .netcore.

I have a model with the following properties:

public class Criterial {
  [Required]
  public string Field { get; set; }

  [Required]
  public Operator Operator { get; set; }

  [Required]
  public string Value { get; set; }

  public bool Result { get; set; }
}

public enum Operator {
    greater_than,
    equal_to,
    lower_than
}

I’m trying to use enum to restrict the values that the Operator propertie can receive, but when I make a POST request to the API I got the following scenario:

POST Request Body:

"criterials": [
    {
        "field": "amount",
        "operator": "greater_than",
        "value": "50"
    }
]

Response from the API:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|7e53377-444fa4a723ac655c.",
    "errors": {
        "$.criterials[0].operator": [
            "The JSON value could not be converted to LeagueOfFateApi.Models.Operator. Path: $.criterials[0].operator | LineNumber: 5 | BytePositionInLine: 26."
        ]
    }
}

Searching about the issue on the internet I found the [JsonConverter(typeof(JsonStringEnumConverter))] Data Annotation.

So I added it to my code and the issue was “solved”:

[Required]
[JsonConverter(typeof(JsonStringEnumConverter))]
public Operator Operator { get; set; }

New response from the API:

"criterials": [
    {
        "field": "amount",
        "operator": "greater_than",
        "value": "50",
        "result": false
    }
]

The problem is: in my MongoDB collection a new document was saved with the int value 0 of the enums, and not the string value “greater_than”:

"Criterials" : [
    {
        "Field" : "amount",
        "Operator" : 0,
        "Value" : "50",
        "Result" : false
    }
]

Besides, another problem is that the “criterial” field can receive any int value with no restrictions.

Is there any other practical way to restrict a string’s options without using enums? Or is there anything I can add to this solution using enums?

Thank you very much for your attention and your time!

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Answers:

Method 1

Answers:

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Method 1

According to your description, I suggest you could write custom set and get method for the Operator property.

You could set the Operator’s type is string and use Enum.IsDefined to check the Operator value is enum Operator or not.

More details, you could refer to below codes:

public class Criterial
{
    [Required]
    public string Field { get; set; }

    private string _Operator;

    [Required]
    public string Operator {
        get {
            return this._Operator;
        }
        set {
            if (Enum.IsDefined(typeof(Operator), value))
            {
                this._Operator = value;
            }
            else
            {
                this._Operator = "Error you used wrong string";
            }
        } 
    
    }

    [Required]
    public string Value { get; set; }

    public bool Result { get; set; }
}

public enum Operator
{
    greater_than,
    equal_to,
    lower_than
}

Result:

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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