如何重新格式化 CSV 文件中的 DateTime 值？

Question

我有一个 CSV 文件，其中包含（在其他字段中）（可为空）格式类似于“2021-11-20 14:16:52.255421”的 DateTime 值我想去掉毫秒或其他任何格式那就是。

我试过这样，但不知何故日期格式保持不变：

    var csvConfiguration = new CsvConfiguration(CultureInfo.InvariantCulture);
    csvConfiguration.HasHeaderRecord = true;
    csvConfiguration.Delimiter = ";";
    csvConfiguration.TrimOptions = TrimOptions.Trim;
    
    Record[] records;

    using (var reader = new StreamReader(CsvPath, Encoding.UTF8))
    using (var csv = new CsvReader(reader, csvConfiguration))
    {
        records = csv.GetRecords<Record>().ToArray();
    }

    using (var writer = new StreamWriter($@"reformatted.csv"))
    using (var csv = new CsvWriter(writer, CultureInfo.CurrentCulture))
    {
        //I have also tried with these options, but it doesn't help either
        //var options = new TypeConverterOptions { Formats = new[] { "yyyy-MM-dd HH:mm:ss" } };
        //csv.Context.TypeConverterOptionsCache.AddOptions<DateTime>(options);
        csv.WriteRecords(records.Where(x => x.Memo != null));
    }

// "mbox_id";"email_address";"created";"updated";"created_by";"memo";
class Record
{
    [Name("mbox_id")]
    public string MailboxId { get; set; }
    
    [Name("email_address")]
    public string EmailAddress { get; set;}
    
    [Name("created")]
    public DateTime? Created { get; set; }
    
    [Name("updated")]
    public DateTime? Updated { get; set; }
    
    [Name("created_by")]
    public string CreatedBy { get; set;}
    
    [Name("memo")]
    public string Memo { get; set; }
}

我做错了什么？我真的不明白 CsvWriter 怎么会知道输入格式...

Answer 1

你的问题是，由于你的属性是 DateTime? 类型，你必须显式地为 DateTime? 和 DateTime:

注册一个类型转换器

csv.Context.TypeConverterOptionsCache.AddOptions<DateTime?>(options);
csv.Context.TypeConverterOptionsCache.AddOptions<DateTime>(options);

演示 fiddle #1 here.

如果这种情况经常出现，您可以为 TypeConverterOptionsCache 创建一个扩展方法，如下所示：

public static class TypeConverterOptionsCacheExtensions
{
    public static void AddOptionsForTypeAndNullable(this TypeConverterOptionsCache cache, Type type, TypeConverterOptions options)
    {
        if (type == null || cache == null)
            throw new ArgumentNullException();

        if (!type.IsValueType)
        {
            cache.AddOptions(type, options);
        }
        else
        {
            var underlying = Nullable.GetUnderlyingType(type) ?? type;
            var nullable = typeof(Nullable<>).MakeGenericType(underlying);
            cache.AddOptions(underlying, options);
            cache.AddOptions(nullable, options);
        }
    }


    public static void AddOptionsForTypeAndNullable<T>(this TypeConverterOptionsCache cache, TypeConverterOptions options) where T : struct
        => cache.AddOptionsForTypeAndNullable(typeof(T), options);
}

然后做：

csv.Context.TypeConverterOptionsCache.AddOptionsForTypeAndNullable<DateTime>(options);

演示 fiddle #2 here.

如何重新格式化 CSV 文件中的 DateTime 值？

How to reformat DateTime values in CSV file?

c#

csv

csvhelper