OData V4 modify $filter on server side

Remove [EnableQuery] attribute, your scenario should work, because after using this attribute, OData/WebApi will apply your original query option after you return data in controller, if you already apply in your controller method, then you shouldn’t use that attribute.

But if your query option contains $select, those code are not working because the result’s type is not Product, we use a wrapper to represent the result of $select, so I suggest you use try this:

Make a customized EnableQueryAttribute

public class MyEnableQueryAttribute : EnableQueryAttribute
{
    public override IQueryable ApplyQuery(IQueryable queryable, ODataQueryOptions queryOptions)
    {
        if (queryOptions.Filter != null)
        {
            queryOptions.ApplyTo(queryable);
            var url = queryOptions.Request.RequestUri.AbsoluteUri;

            url = url.Replace("$filter=Id%20eq%201", "$filter=Id%20eq%202");
            var req = new HttpRequestMessage(HttpMethod.Get, url);

            queryOptions = new ODataQueryOptions(queryOptions.Context, req);
        }

        return queryOptions.ApplyTo(queryable);
    }
}

Use this attribute in your controller method

[MyEnableQueryAttribute]
public IHttpActionResult Get()
{
    return Ok(_products);
}

Hope this can solve your problem, thanks!

Fan.