Ad hoc Simple.Data queries

AdHocQuery.cs

    [HttpGet]
    public virtual ActionResult Query()
    {
      var result = entity.All();
      var q      = Request.QueryString;

      if (null != q["select"])
      {
        var selection = q["select"].Split(',').Select(col => entity[col] as SimpleReference).ToArray();
        result = result.Select(selection);
      }

      dynamic filter = null;

      var operations = new Dictionary<string, Func<dynamic, dynamic, dynamic>>() {
        {"isset", (x, y) => x != null },
        {"isnotset", (x, y) => x == null },
        {"equals", (x, y) => x == y },
        {"notequals", (x, y) => x != y },
        {"lessthan", (x, y) => x < y },
        {"lessthanorequal", (x, y) => x <= y },
        {"greaterthan", (x, y) => x > y },
        {"greaterthanorequal", (x, y) => x >= y },
        {"like", (x, y) => x.Like(y) },
      };

      Action<dynamic> addFilter = (match) => {
        if (null == filter)
          filter = match;
        else
          filter = filter && match;
      };

      operations.Keys.ForEach(key => {
        var givenFilter = q[key];
        if (null != givenFilter)
          givenFilter.Split(',').ForEach(pair => {
            var values = pair.Split('=');
            var value = values.Length == 2 ? values[1] : null;
            addFilter(operations[key](entity[values[0]], value));
          });
      });

      if (null != filter) result = result.Where(filter);

      if (null != q["orderBy"]) result = result.OrderBy(entity[q["orderBy"]]);
      if (null != q["orderByDescending"]) result = result.OrderByDescending(entity[q["orderByDescending"]]);

      if (null != q["skip"]) result = result.Skip(int.Parse(q["skip"]));
      if (null != q["take"]) result = result.Take(int.Parse(q["take"]));

      if (null != q["with"]) result = result.With(q["with"]);

      return Json(result, JsonRequestBehavior.AllowGet);
    }