如何更改datatable中日期列的日期格式？ [英] How to change date format for the date column in datatable?

问题描述

我正在从数据库填充datable。
它包含两个字段： DATE ， TIME

两个字段都是 datetime 列

我想迭代数据表并更改日期格式 DATE 列即 dd / MM / yyyy

  int i = 0; 
 string d =; 
 foreach（dataTable.Rows中的DataRow dr）
 {
 d = dr [DATE]。ToString（）; 
 DateTime date = Convert.ToDateTime（d）; 
 d = date.ToString（dd / MM / yyyy）; 
 dataTable.Rows [i] [DATE] = d; 
 i ++; 
} 
  

我收到以下错误

字符串未被识别为有效的DateTime。

在DATE列中无法存储< 15/02/2015> 。预期类型是DateTime。如何实现？

解决方案

，你没有告诉我们你创建了你的 dataTable ，但这里是我的想法..

> DATE 和 TIME 列是 DateTime ，那么您需要提供它们 Datetime 值。不是 string 。

在.NET Framework中， DateTime 结构没有任何隐式格式。它只是具有日期和时间值。当您尝试格式化时，您可以获得它的字符串表示。这就是为什么 15/02/2015 将是一个字符串，而不是一个 DateTime 。

您的 Convert.ToDateTime您将获得 FormatException 方法可能是因为您的 d 值不是的az4se3k1（v = vs.110）.aspxrel =nofollow .globalization.cultureinfo.currentculture％28v = vs.110％29.aspxrel =nofollow> CurrentCulture 。您可以使用自定义日期和时间解析，使用 DateTime.ParseExact 或 DateTime.TryParseExact 方法。

  string s =15/02/2015; 
 DateTime dt; 
 if（DateTime.TryParseExact（s，dd / MM / yyyy，CultureInfo.InvariantCulture，
 DateTimeStyles.None，
 out dt））
 {
控制台.WriteLine（dt）; 
} 
  

即使你这样做，你为什么要保持 datetime 键入列中的字符串值？这完全没有意义 。即使你这样做，因为 .Rows 返回一个 DataRowCollection ，你可能会得到集合被修改;枚举操作可能无法执行错误，因为您尝试在迭代时修改集合。

我建议您创建另一个 DataTable 为您的字符串值，并将它们添加到 DateTime 值字符串表示形式为 dd / MM / yyyy 格式如;

  int i = 0; 
 string d =; 
 var stringDataTable = new DataTable（）; 
 stringDataTable.Columns.Add（DATE，typeof（String））; 
 stringDataTable.Columns.Add（TIME，typeof（String））; 
 
 foreach（dataTable.Rows中的DataRow）
 {
d =（（DateTime）dr [DATE]）ToString（dd / MM / yyyy，CultureInfo不变文化）; 
 stringDataTable.Rows [i] [DATE] = d; 
 i ++; 
} 
  

I am filling the datable from database. It contains two field: DATE, TIME

Both the fields are datetime column

I want to iterate through the datatable and change the date format for the DATE column i.e dd/MM/yyyy

int i = 0;
string d="";
foreach (DataRow dr in dataTable.Rows)
{
    d = dr["DATE"].ToString();
    DateTime date = Convert.ToDateTime(d);
    d = date.ToString("dd/MM/yyyy");
    dataTable.Rows[i]["DATE"] = d;
    i++;
}

I get the following error

String was not recognized as a valid DateTime.

Couldn't store <15/02/2015> in DATE Column. Expected type is DateTime. How can I achieve it?

解决方案

Well, you didn't tell us how you create your dataTable but here my thought..

If your both DATE and TIME columns are DateTime, then you need to supply them Datetime values. Not string.

In .NET Framework, DateTime structure doesn't have any implicit format. It just have date and time values. You get it's string representation when you try to format it. That's why 15/02/2015 will be a string in your case, not a DateTime.

You get FormatException on your Convert.ToDateTime method probably because your d value was not a standard date and time format for your CurrentCulture. You can use custom date and time parsing with using DateTime.ParseExact or DateTime.TryParseExact methods.

string s = "15/02/2015";
DateTime dt;
if(DateTime.TryParseExact(s, "dd/MM/yyyy", CultureInfo.InvariantCulture,
                          DateTimeStyles.None,
                          out dt))
{
    Console.WriteLine(dt);
}

Even if you do that, why do you wanna keep string values in a datetime typed column? That doesn't make sense at all. Even if you do that, since .Rows returns a DataRowCollection, you probably will get Collection was modified; enumeration operation may not execute error since you try to modify your collection while you iterating it.

I suggest you to create another DataTable for your string values and add them to your DateTime values string representation as dd/MM/yyyy format like;

int i = 0;
string d = "";
var stringDataTable = new DataTable();
stringDataTable.Columns.Add("DATE", typeof(String));
stringDataTable.Columns.Add("TIME", typeof(String));

foreach(DataRow dr in dataTable.Rows)
{
   d = ((DateTime)dr["DATE"]).ToString("dd/MM/yyyy", CultureInfo.InvariantCulture);
   stringDataTable.Rows[i]["DATE"] = d;
   i++;
}

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