此方法用于将当前DateTime对象的值转换为其等效的字符串表示形式。此方法的重载列表中共有4种方法：
- ToString(String，IFormatProvider)
- ToString(字符串)
- ToString(IFormatProvider)
- ToString()
在这里，我们将只讨论前两种方法。
ToString(String，IFormatProvider)
此方法用于使用指定的格式和区域性特定的格式信息将当前DateTime对象的值转换为其等效的字符串表示形式。
Syntax: public string ToString (string format, IFormatProvider provider);
Parameters:
format: A standard or custom date and time format string.
provider: An object that supplies culture-specific formatting information.
Return Value: This method returns a string representation of the value of the current DateTime object as specified by format and provider.
例外情况：
- FormatException：如果format的长度为1，并且不是为DateTimeFormatInfo定义的格式说明字符之一，或者该格式不包含有效的自定义格式模式。
- ArgumentOutOfRangeException：如果日期和时间超出提供者使用的日历支持的日期范围。
下面的程序说明了DateTime.ToString(String，IFormatProvider)方法的用法：
范例1：
// C# program to demonstrate the
// DateTime.ToString(String,
// IFormatProvider) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// creating object of CultureInfo
CultureInfo cultures =
CultureInfo.CreateSpecificCulture("de-DE");
// declaring and intializing String array
string[] format = {"d", "D", "f", "F", "g", "G",
"m", "o", "r","s", "t" };
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++)
{
get(format[j], cultures);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format,
CultureInfo cultures)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(2008, 10,
1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format, cultures);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
01.10.2008
Mittwoch, 1. Oktober 2008
Mittwoch, 1. Oktober 2008 17:04
Mittwoch, 1. Oktober 2008 17:04:32
01.10.2008 17:04
01.10.2008 17:04:32
1. Oktober
2008-10-01T17:04:32.0000000
Wed, 01 Oct 2008 17:04:32 GMT
2008-10-01T17:04:32
17:04
示例2：对于FormatException
// C# program to demonstrate the
// DateTime.ToString(String,
// IFormatProvider) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// creating object of CultureInfo
CultureInfo cultures =
CultureInfo.CreateSpecificCulture("de-DE");
// declaring and intializing String array
string[] format = {"d", "D", "f", "F", "g", "G",
"s", "x"};
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++)
{
get(format[j], cultures);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.WriteLine("format does not contain "+
"a valid custom format pattern.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format,
CultureInfo cultures)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(2008,
10, 1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format, cultures);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
01.10.2008
Mittwoch, 1. Oktober 2008
Mittwoch, 1. Oktober 2008 17:04
Mittwoch, 1. Oktober 2008 17:04:32
01.10.2008 17:04
01.10.2008 17:04:32
2008-10-01T17:04:32
format does not contain a valid custom format pattern.
Exception Thrown: System.FormatException
示例3：对于ArgumentOutOfRangeException
// C# program to demonstrate the
// DateTime.ToString(String,
// IFormatProvider) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// creating object of CultureInfo
CultureInfo cultures =
CultureInfo.CreateSpecificCulture("ar-SA");
// declaring and intializing String array
string[] format = {"d", "D", "f", "F",
"g", "G","s" };
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++) {
get(format[j], cultures);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.WriteLine("format does not contain "+
"a valid custom format pattern.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.WriteLine("The date and time is outside the range of dates"
+ "supported by the calendar used by ar-SA");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format,
CultureInfo cultures)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(2999,
10, 1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format, cultures);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
The date and time is outside the range of datessupported by the calendar used by ar-SA
Exception Thrown: System.ArgumentOutOfRangeException
ToString(String)方法
此方法用于使用指定的格式和当前区域性的格式约定将当前DateTime对象的值转换为其等效的字符串表示形式。
Syntax: public string ToString (string format);
Here it takes a standard or custom date and time format string.
Return Value: This method returns a string representation of value of the current DateTime object as specified by format.
例外情况：
- FormatException：如果format的长度为1，并且不是为DateTimeFormatInfo定义的格式说明字符之一，或者该格式不包含有效的自定义格式模式。
- ArgumentOutOfRangeException：如果日期和时间超出当前区域性使用的日历支持的日期范围。
下面的程序说明了ToString(String)方法的用法：
范例1：
// C# program to demonstrate the
// DateTime.ToString(String) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// declaring and intializing String array
string[] format = {"d", "D", "f", "F", "g",
"G", "m", "o", "r","s", "t" };
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++)
{
get(format[j]);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(2008,
10, 1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
10/01/2008
Wednesday, 01 October 2008
Wednesday, 01 October 2008 17:04
Wednesday, 01 October 2008 17:04:32
10/01/2008 17:04
10/01/2008 17:04:32
October 01
2008-10-01T17:04:32.0000000
Wed, 01 Oct 2008 17:04:32 GMT
2008-10-01T17:04:32
17:04
示例2：对于FormatException
// C# program to demonstrate the
// DateTime.ToString(String) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// declaring and intializing String array
string[] format = {"d", "D", "f", "F",
"g", "G", "s", "x" };
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++)
{
get(format[j]);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.WriteLine("format does not contain "+
"a valid custom format pattern.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(2008,
10, 1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
10/01/2008
Wednesday, 01 October 2008
Wednesday, 01 October 2008 17:04
Wednesday, 01 October 2008 17:04:32
10/01/2008 17:04
10/01/2008 17:04:32
2008-10-01T17:04:32
format does not contain a valid custom format pattern.
Exception Thrown: System.FormatException
示例3：对于ArgumentOutOfRangeException
// C# program to demonstrate the
// DateTime.ToString(String) Method
using System;
using System.Globalization;
class GFG {
// Main Method
public static void Main()
{
try {
// declaring and intializing String array
string[] format = {"d", "D", "f", "F",
"g", "G","s" };
// calling get() Method
Console.WriteLine("Converts the value of the current"
+ "DateTime object to its equivalent string");
for (int j = 0; j < format.Length; j++)
{
get(format[j]);
}
}
catch (FormatException e)
{
Console.WriteLine("\n");
Console.WriteLine("format does not contain "+
"a valid custom format pattern.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("\n");
Console.WriteLine("The date and time are outside the range of dates "
+ "supported by the calendar used by the current culture.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining get() method
public static void get(string format)
{
// Define date to be displayed.
DateTime dateToDisplay = new DateTime(9999,
13, 1, 17, 4, 32);
// converting DateTime to specified string
string val = dateToDisplay.ToString(format);
// display the converted ulong value
Console.WriteLine(" {0} ", val);
}
}
输出：
Converts the value of the currentDateTime object to its equivalent string
The date and time are outside the range of dates supported by the calendar used by the current culture.
Exception Thrown: System.ArgumentOutOfRangeException
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.datetime.tostring?view=netframework-4.7.2