我們可以在CsvHelper的屬性中同時使用Index和Name屬性嗎？

我是使用CsvHelperAPI 撰寫 CSV 檔案的新手。我已閱讀入門幫助主題。

我需要創建一個只定義了標題的空 CSV 檔案。這樣用戶就可以從此模板檔案開始并填充資料。

我知道如何手動創建文本檔案并自己手動完成。但是，由于我的課程具有讀取 CSV 的屬性，我想知道是否可以利用它來做相反的事情？

我在那里看到了一個例子，WriteHeader所以我想出了：

public void CreateEmptyHistoryFile(string path)
{
    using (var writer = new StreamWriter(path))
    using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
    {
        csv.WriteHeader<GenericHistory>();
    }
}    

但是如果可以將這兩個屬性都添加到我的屬性中，我找不到它的檔案：

[Index(1)]
[Name(“xxx”)]
Public string Yyy …

鏈接的文章說：

還記得我們如何不能依賴 .NET 中的屬性順序嗎？如果我們正在撰寫一個有標題的類，那沒關系，只要我們稍后使用標題讀取即可。如果我們想在 CSV 檔案中定位標題，我們需要指定一個索引來保證它的順序。建議在寫入時始終設定索引。

• 當我使用名稱屬性閱讀時。
• 當我撰寫帶有標題的空檔案時，我邏輯上希望按順序呈現它們（只是為了清楚起見）。

說得通？我們可以混合使用這兩個屬性嗎？

更新

我想知道那個關于屬性順序的建議是否過時了？

我剛剛運行了我的代碼，輸出按寫入順序排列（我沒有Index添加任何屬性）。

更新

我的班級有 82 個屬性，我嘗試為Index每個屬性添加一個屬性。當我嘗試閱讀時，我遇到了一個例外：

  <LogEntry Date="2022-01-22 18:38:03" Severity="Exception" Source="MSAToolsLibrary.Importer.Importer.ImportHistoryFromGeneric" ThreadId="1">
    <Exception Type="CsvHelper.TypeConversion.TypeConverterException" Source="CsvHelper.TypeConversion.DefaultTypeConverter.ConvertFromString">
      <Message>The conversion cannot be performed.
    Text: 'Andrew Truckle'
    MemberType: System.Int32
    TypeConverter: 'CsvHelper.TypeConversion.Int32Converter'
IReader state:
   ColumnCount: 0
   CurrentIndex: 4
   HeaderRecord:
["Week","MidweekMeeting","WeekendMeeting","NumClasses","Host","Cohost","Chairman","AuxCounsellor1","AuxCounsellor2","PrayerOpen","Treasures_Name","Treasures_Theme","Treasures_Method","Gems_Name","Teaching","Teaching_Class1_Name","Teaching_Class2_Name","Teaching_Class3_Name","BibleReading_Study","StudentItem1_Study","StudentItem2_Study","StudentItem3_Study","StudentItem4_Study","StudentItem1_Description","StudentItem2_Description","StudentItem3_Description","StudentItem4_Description","BibleReading_Class1_Name","BibleReading_Class2_Name","BibleReading_Class3_Name","StudentItem1_Class1_Name","StudentItem1_Class1_Assistant","StudentItem2_Class1_Name","StudentItem2_Class1_Assistant","StudentItem3_Class1_Name","StudentItem3_Class1_Assistant","StudentItem4_Class1_Name","StudentItem4_Class1_Assistant","StudentItem1_Class2_Name","StudentItem1_Class2_Assistant","StudentItem2_Class2_Name","StudentItem2_Class2_Assistant","StudentItem3_Class2_Name","StudentItem3_Class2_Assistant","StudentItem4_Class2_Name","StudentItem4_Class2_Assistant","StudentItem1_Class3_Name","StudentItem1_Class3_Assistant","StudentItem2_Class3_Name","StudentItem2_Class3_Assistant","StudentItem3_Class3_Name","StudentItem3_Class3_Assistant","StudentItem4_Class3_Name","StudentItem4_Class3_Assistant","Living1_Name","Living1_Theme","Living1_Method","Living2_Name","Living2_Theme","Living2_Method","Living3_Name","Living3_Theme","Living3_Method","CBS_Conductor","CBS_Reader","PrayerClose","Weekend_Host","Weekend_Cohost","Weekend_Chairman","Weekend_PrayerOpen","Weekend_PT_Speaker","Weekend_PT_Theme","Weekend_PT_Number","Weekend_PT_Hospitality","Weekend_PT_Interpreter","Weekend_AT1_Name","Weekend_AT2_Name","Weekend_WT_Conductor","Weekend_WT_Reader","Weekend_WT_BibleVersesReader","Weekend_PrayerClose","Weekend_Misc"]
IParser state:
   ByteCount: 0
   CharCount: 2289
   Row: 2
   RawRow: 2
   Count: 82
   RawRecord:
27/01/2020,Y,Y,1,...

</Message>
      <StackTrace>   at CsvHelper.TypeConversion.DefaultTypeConverter.ConvertFromString(String text, IReaderRow row, MemberMapData memberMapData)
   at CsvHelper.TypeConversion.Int32Converter.ConvertFromString(String text, IReaderRow row, MemberMapData memberMapData)
   at lambda_method(Closure )
   at CsvHelper.Expressions.RecordCreator.Create[T]()
   at CsvHelper.CsvReader.&lt;GetRecords&gt;d__87`1.MoveNext()
   at MSAToolsLibrary.Importer.Importer.ImportHistoryFromGeneric()</StackTrace>
    </Exception>
  </LogEntry>

出于隱私原因，我已洗掉資料中的姓名。我注意到它參考當前索引 4 并執行整數轉換。如您所見，該值為1。在閱讀課上：

[Index(4)]
public int NumClasses { get => HistoryWeek.NumClasses; set => HistoryWeek.NumClasses = value; }

正如我所說，如果我洗掉所有[Index(..)]我的閱讀代碼仍然有效。但是，如果我重新引入所有索引值，則會失敗。

uj5u.com熱心網友回復：

我通常發現它的順序與您的類中宣告的屬性的順序相同。但是，如果您想確定它們按特定順序排列，我會同時使用它們。

Type.GetProperties 方法

該GetProperties方法不按特定順序回傳屬性，例如字母順序或宣告順序。您的代碼不得依賴于回傳屬性的順序，因為該順序會有所不同。

你可以試試這個例子，看看Name和Index屬性在使用CsvWriter.

void Main()
{
    using (var csv = new CsvWriter(Console.Out, CultureInfo.InvariantCulture))
    {
        csv.WriteHeader<Foo>();
    }
}

public class Foo
{
    [Name("Identity")]
    [Index(1)]
    public int Id { get; set; }
    [Name("FirstName")]
    [Index(0)]
    public string Name { get; set; }
}

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