How to check if a property is $select-ed?

Question

I am building an OData web API, and I am trying to implement this function to determine whether a given property should be included in a GET response based on the $select value in the query:

bool IsPropertySelected(ODataQueryOptions options, string propertyName)

Browsing docs for ODataQueryOptions, there is not an obvious way to do this. I have seen that the library will apply the $select clause automatically, but this happens after the response object is generated with all the properties. Some properties are expensive to calculate, so I want to avoid this cost for any properties that are not $select-ed.

For example, with an entity schema like:

class Foo
{
    public string a {get; set;} // From data source A
    public string b {get; set;} // From data source B
    public string c {get; set;} // Aggregated from both data sources
}

The controller method would look something like

public async Task<Foo> GetFoo(string id, ODataQueryOptions options)
{
    var result = new Foo();

    bool needDataFromA = (new List { "a", "c" }).Any(x => IsPropertySelected(options, x));
    bool needDataFromB = (new List { "b", "c" }).Any(x => IsPropertySelected(options, x));

    if (needDataFromA && needDataFromB)
    {
        // get data from A and set result.a
        // get data from B and set result.b
        // set result.c
    }
    else if (needDataFromA)
    {
        // get data from A and set result.a
    }
    else if (needDataFromB)
    {
        // get data from B and set result.b
    }
    return result;
}