How can I capture included property names in a JSON web api request with asp.net core?

Question

I am building an asp.net core web api and I need to keep track of properties that were actually included in a JSON body, since .NET doesnt have the concept of undefined as in javascript, just null.

I created an interface which all of my models implement which is just a string array called IncludedProperties:

string[] IncludedProperties {get; set;}

I might have models which have more of these models nested inside. Any time I am deserializing one of these models, I want it to populate this list of IncludedProperties.

For example, in my controller:

public async Task<ActionResult> PatchModel([FromRoute]Guid id, [FromBody] RootModel model) { ... }

And classes are is defined as:

public class RootModel : IIncludedProperties
{
    public string Name { get; set;}
    public string Description {get; set;}
    public NestedModel SubEntity { get; set;}
    public string[] IncludedProperties {get; set;}
}

public class NestedModel : IIncludedProperties
{
   public string Name {get; set;}
   public decimal Value {get; set;}
   public string[] IncludedProperties {get; set;}
}

If the JSON body is as follows:

{
    "Name": "New Entity 01",
    "SubEntity": {
        "Name": "Child Entity 01",
        "Value": 0.5
    }
}

The included properties for the root would be [ "Name", "SubEntity"] and the included properties for the nested model would be [ "Name", "Value" ].

I am going through the documentation from Microsoft on custom converters for JSON, but it seems I will need to rewrite the entire json converter just to add in a bit of extra functionality. Is there any way I could "plug in" to the existing converter, just to capture the included property names?

You want InclucedProperties to be an array that holds the names or values, of the attributes of the json object? — Arturo Lozano, Mar 28 '20 at 01:19

Củ Su Hào · Answer 1 · 2020-03-28T03:21:43.763

This can be solved with reflection and recursion. If you don't mind adding one more line inside each controller, you can call this function after model binding:

void PopulateIncludedProperties(IIncludedProperties obj)
{
    var properties = obj.GetType().GetProperties().ToList();
    obj.IncludedProperties = properties
        .Where(p => p.Name != "IncludedProperties" && p.GetValue(obj) != null)
        .Select(p => p.Name).ToArray();

    foreach (var prop in properties)
    {
        var value = prop.GetValue(obj);
        if (value is IIncludedProperties includedPropValue)
        {
            PopulateIncludedProperties(includedPropValue);
        }
    }
}

Please customize yourself if you want to populate IncludedProperties of an IEnumerable<IIncludedProperties>

How can I capture included property names in a JSON web api request with asp.net core?

1 Answers1