How to flatten nested dictionaries in a class using LINQ

The closest solution to what I was looking for is this thread How to flatten nested objects with linq expression

But I am getting error when trying this approach

The type arguments for the 'System.Linq.Enumerable.SelectMany (System.Collections.Generic.IEnumerable, System.Func>)' method cannot be deprecated. Try to specify type arguments explicitly.

My code:

var aa = t.data.SelectMany(x => 
                    x.Value.innerData.SelectMany(y => new { /*Error at this SelectMany*/
                    url = x.Key,
                    disp = x.Value.disp,
                    date = y.Key,
                    count = y.Value.count,
                    rank = y.Value.rank,
       }));

      

        
        
        
      

    

My classes:

public class TData {
    public Dictionary<string, TDetail> data { get; set; }
}

public class TDetail {
    public string disp { get; set; }

    [Newtonsoft.Json.JsonProperty("data")]
    public Dictionary<string, Metrics> innerData { get; set; }

}

public class Metrics {
    public string count { get; set; }
    public string rank { get; set; }
}

      

        
        
        
      

    

The JSON I receive from the third party API looks like this:

{
  "data": {
    "abc.com": {
      "disp": "#712176",
      "data": {
        "2015-02-08": {
          "count": 4,
          "rank": 5.8
        },
        "2015-02-23": {
          "count": 3,
          "rank": 8.3
        },
        "2015-03-14": {
          "count": 5,
          "rank": 3.7
        }
      }
    },
    "nbc.com": {
      "disp": "#822176",
      "data": {
        "2015-02-08": {
          "count": 3,
          "rank": 5.5
        },
        "2015-02-23": {
          "count": 5,
          "rank": 8.4
        },
        "2015-03-14": {
          "count": 7,
          "rank": 4.7
        }
      }
    }
  }
}

      

        
        
        
      

    

How can I explicitly specify the type arguments in this case? Thank.