Csharp 如果使用LINQ的值为空，则C#不使用GroupBy进行聚合

我有一个列表，如果LineId是相同的，我将它们合并在一起.这一逻辑在所有情况下都适用，只有一种情况除外.在这里，这LineId可以是""或null，如果是这样，我不想合并它.

当LineId是""或null时，我怎么能不合并查询中的列表？

代码:

var groupedLines = lines
    .GroupBy(line => line.LineId)
    .Select(linesGroup => linesGroup.Aggregate((firstLine, nextLine) =>
    {
        // Logic is working as expected

        return firstLine;
    })).ToList();

我试着追随，但它仍然融合在一起

.GroupBy(line => !string.IsNullOrEmpty(line.LineId) )

示例1:(按预期工作)

输入

{
  "Lines": [
    {
      "Id": "1",
      "AccountingTotal": 10.2,
      "Description": "Description 1",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": "101" <-- Merge because it is same
    },
    {
      "Id": "2",
      "AccountingTotal": 10,
      "Description": "Description 2",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": "101" <-- Merge because it is same
    }
  ]
}

输出

{
  "Lines": [
    {
      "Id": "1|2",
      "AccountingTotal": 20.2,
      "Description": "Description 1|Description 1",
      "Price": "20.00",
      "Total": "20.00",
      "LineId": "101"
    }
  ]
}

示例2:(未按预期工作)

输入

{
  "Lines": [
    {
      "Id": "1",
      "AccountingTotal": 10.2,
      "Description": "Description 1",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": "" <-- Do not merge if this is "" or null
    },
    {
      "Id": "2",
      "AccountingTotal": 10,
      "Description": "Description 2",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": "" <-- Do not merge if this is "" or null
    }
  ]
}

预期结果

{
  "Lines": [
    {
      "Id": "1",
      "AccountingTotal": 10.2,
      "Description": "Description 1",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": ""
    },
    {
      "Id": "2",
      "AccountingTotal": 10,
      "Description": "Description 2",
      "Price": "10.00",
      "Total": "10.00",
      "LineId": "" 
    }
  ]
}

实际结果

{
  "Lines": [
    {
      "Id": "1|2",
      "AccountingTotal": 20.4,
      "Description": "Description 1|Description 2",
      "Price": "20.00",
      "Total": "20.00",
      "LineId": ""
    }
  ]
}