如何在特定字段上使用map.tryfind?

所以我将数据映射到一个记录,它显示在底部。但问题是下面指定的代码行。我试图用Map.TryFind函数来索引一张地图并在该地图中返回一个字段,但是它正在输出错误:

Practice2.fsx(299,49): error FS0039: The field, constructor or member 'GrossIncome' is not defined.

我怎样才能成功地做到这一点呢?所用类型的代码如下。

type GeneralInfo =
    { State : State
      GrossIncome : int }

type FamilyFile = 
    { State : State
      Pets : int
      NumberofChildren : int
      NumberofMembers : int }

type AllData = 
    { State = State
      Month = Month
      Pets  = int
      Children = int
      GrossIncome = int Option }

实例 familyMap 和 generalMap :

let generalinfo =
   GeneralCsv.GetSample().Rows
    |> Seq.map (fun row -> 
        { State = row.State |> State
          GrossIncome = row.income })

let generalMap =
    generalinfo
    |> Seq.map (fun x -> x.State,x)
    |> Map.ofSeq

let familyparse=
    FamilyCsv.GetSample().Rows
    |> Seq.map (fun row -> 
        { State = row.State |> State
          Pets = row.pets
          NumberofChildren = row.children
          NumberofMembers = row.familymem  })

let familyMap =
    familyparse
    |> Seq.map (fun x -> x.State,x)
    |> Map.ofSeq

let mapfunc =
    dataMap
    |> Seq.ofList
    |> Seq.map(fun (state,rows) ->
        { State = state
          Month = rows.Month
          Pets = familyMap.[state].Pets
          Children = familyMap.[state].NumberofChildren 
          GrossIncome = generalMap.TryFind(state).GrossIncome <-- Problem Line
          Family = familyMap.[state].NumberofMembers
        })
    |> List.ofSeq