DateTime.TryParseExact 方法

public:
 static bool TryParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, IFormatProvider ^ provider, System::Globalization::DateTimeStyles style, [Runtime::InteropServices::Out] DateTime % result);

public static bool TryParseExact (ReadOnlySpan<char> s, ReadOnlySpan<char> format, IFormatProvider? provider, System.Globalization.DateTimeStyles style, out DateTime result);

public static bool TryParseExact (ReadOnlySpan<char> s, ReadOnlySpan<char> format, IFormatProvider provider, System.Globalization.DateTimeStyles style, out DateTime result);

static member TryParseExact : ReadOnlySpan<char> * ReadOnlySpan<char> * IFormatProvider * System.Globalization.DateTimeStyles * DateTime -> bool

Public Shared Function TryParseExact (s As ReadOnlySpan(Of Char), format As ReadOnlySpan(Of Char), provider As IFormatProvider, style As DateTimeStyles, ByRef result As DateTime) As Boolean

參數

傳回

Boolean

如果 s 轉換成功，則為 true，否則為 false。true if s was converted successfully; otherwise, false.

public:
 static bool TryParseExact(ReadOnlySpan<char> s, cli::array <System::String ^> ^ formats, IFormatProvider ^ provider, System::Globalization::DateTimeStyles style, [Runtime::InteropServices::Out] DateTime % result);

public static bool TryParseExact (ReadOnlySpan<char>? s, string[] formats, IFormatProvider provider, System.Globalization.DateTimeStyles style, out DateTime result);

public static bool TryParseExact (ReadOnlySpan<char> s, string[] formats, IFormatProvider provider, System.Globalization.DateTimeStyles style, out DateTime result);

static member TryParseExact : ReadOnlySpan<char> * string[] * IFormatProvider * System.Globalization.DateTimeStyles * DateTime -> bool

Public Shared Function TryParseExact (s As ReadOnlySpan(Of Char), formats As String(), provider As IFormatProvider, style As DateTimeStyles, ByRef result As DateTime) As Boolean

參數

傳回

Boolean

如果 true 參數轉換成功，則為 s，否則為 false。true if the s parameter was converted successfully; otherwise, false.

public:
 static bool TryParseExact(System::String ^ s, System::String ^ format, IFormatProvider ^ provider, System::Globalization::DateTimeStyles style, [Runtime::InteropServices::Out] DateTime % result);

public static bool TryParseExact (string s, string format, IFormatProvider provider, System.Globalization.DateTimeStyles style, out DateTime result);

static member TryParseExact : string * string * IFormatProvider * System.Globalization.DateTimeStyles * DateTime -> bool

Public Shared Function TryParseExact (s As String, format As String, provider As IFormatProvider, style As DateTimeStyles, ByRef result As DateTime) As Boolean

參數

傳回

Boolean

如果 s 轉換成功，則為 true，否則為 false。true if s was converted successfully; otherwise, false.

例外狀況

範例

下列範例會示範 DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) 方法。The following example demonstrates the DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) method. 請注意，當參數相等時，無法成功剖析字串 "5/01/2009 8:30 AM"， styles DateTimeStyles.None 因為不允許前置空格 format 。Note that the string " 5/01/2009 8:30 AM" cannot be parsed successfully when the styles parameter equals DateTimeStyles.None because leading spaces are not allowed by format. 此外，字串 "5/01/2009 09:00" 無法以 format "MM/dd/yyyyhh： MM" 成功剖析，因為日期字串不在月份號碼前面，並有前置零，如同 format 需要。Additionally, the string "5/01/2009 09:00" cannot be parsed successfully with a format of "MM/dd/yyyyhh:mm" because the date string does not precede the month number with a leading zero, as format requires.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      CultureInfo enUS = new CultureInfo("en-US");
      string dateString;
      DateTime dateValue;

      // Parse date with no style flags.
      dateString = " 5/01/2009 8:30 AM";
      if (DateTime.TryParseExact(dateString, "g", enUS,
                                 DateTimeStyles.None, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Allow a leading space in the date string.
      if (DateTime.TryParseExact(dateString, "g", enUS,
                                 DateTimeStyles.AllowLeadingWhite, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Use custom formats with M and MM.
      dateString = "5/01/2009 09:00";
      if (DateTime.TryParseExact(dateString, "M/dd/yyyy hh:mm", enUS,
                                 DateTimeStyles.None, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Allow a leading space in the date string.
      if (DateTime.TryParseExact(dateString, "MM/dd/yyyy hh:mm", enUS,
                              DateTimeStyles.None, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Parse a string with time zone information.
      dateString = "05/01/2009 01:30:42 PM -05:00";
      if (DateTime.TryParseExact(dateString, "MM/dd/yyyy hh:mm:ss tt zzz", enUS,
                              DateTimeStyles.None, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Allow a leading space in the date string.
      if (DateTime.TryParseExact(dateString, "MM/dd/yyyy hh:mm:ss tt zzz", enUS,
                              DateTimeStyles.AdjustToUniversal, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      // Parse a string representing UTC.
      dateString = "2008-06-11T16:11:20.0904778Z";
      if (DateTime.TryParseExact(dateString, "o", CultureInfo.InvariantCulture,
                                     DateTimeStyles.None, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);

      if (DateTime.TryParseExact(dateString, "o", CultureInfo.InvariantCulture,
                                 DateTimeStyles.RoundtripKind, out dateValue))
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue,
                           dateValue.Kind);
      else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString);
   }
}
// The example displays the following output:
//    ' 5/01/2009 8:30 AM' is not in an acceptable format.
//    Converted ' 5/01/2009 8:30 AM' to 5/1/2009 8:30:00 AM (Unspecified).
//    Converted '5/01/2009 09:00' to 5/1/2009 9:00:00 AM (Unspecified).
//    '5/01/2009 09:00' is not in an acceptable format.
//    Converted '05/01/2009 01:30:42 PM -05:00' to 5/1/2009 11:30:42 AM (Local).
//    Converted '05/01/2009 01:30:42 PM -05:00' to 5/1/2009 6:30:42 PM (Utc).
//    Converted '2008-06-11T16:11:20.0904778Z' to 6/11/2008 9:11:20 AM (Local).
//    Converted '2008-06-11T16:11:20.0904778Z' to 6/11/2008 4:11:20 PM (Utc).

Imports System.Globalization

Public Module Example
   Public Sub Main()
      Dim enUS As New CultureInfo("en-US") 
      Dim dateString As String
      Dim dateValue As Date
      
      ' Parse date with no style flags.
      dateString = " 5/01/2009 8:30 AM"
      If Date.TryParseExact(dateString, "g", enUS, _
                            DateTimeStyles.None, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
      ' Allow a leading space in the date string.
      If Date.TryParseExact(dateString, "g", enUS, _
                            DateTimeStyles.AllowLeadingWhite, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
      
      ' Use custom formats with M and MM.
      dateString = "5/01/2009 09:00"
      If Date.TryParseExact(dateString, "M/dd/yyyy hh:mm", enUS, _
                            DateTimeStyles.None, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
      ' Allow a leading space in the date string.
      If Date.TryParseExact(dateString, "MM/dd/yyyy hh:mm", enUS, _
                            DateTimeStyles.None, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If

      ' Parse a string with time zone information.
      dateString = "05/01/2009 01:30:42 PM -05:00" 
      If Date.TryParseExact(dateString, "MM/dd/yyyy hh:mm:ss tt zzz", enUS, _
                            DateTimeStyles.None, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
      ' Allow a leading space in the date string.
      If Date.TryParseExact(dateString, "MM/dd/yyyy hh:mm:ss tt zzz", enUS, _
                            DateTimeStyles.AdjustToUniversal, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
           
      ' Parse a string representing UTC.
      dateString = "2008-06-11T16:11:20.0904778Z"
      If Date.TryParseExact(dateString, "o", CultureInfo.InvariantCulture, _
                                     DateTimeStyles.None, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
      
      If Date.TryParseExact(dateString, "o", CultureInfo.InvariantCulture, _
                            DateTimeStyles.RoundtripKind, dateValue) Then
         Console.WriteLine("Converted '{0}' to {1} ({2}).", dateString, dateValue, _
                           dateValue.Kind)
      Else
         Console.WriteLine("'{0}' is not in an acceptable format.", dateString)
      End If
   End Sub
End Module
' The example displays the following output:
'    ' 5/01/2009 8:30 AM' is not in an acceptable format.
'    Converted ' 5/01/2009 8:30 AM' to 5/1/2009 8:30:00 AM (Unspecified).
'    Converted '5/01/2009 09:00' to 5/1/2009 9:00:00 AM (Unspecified).
'    '5/01/2009 09:00' is not in an acceptable format.
'    Converted '05/01/2009 01:30:42 PM -05:00' to 5/1/2009 11:30:42 AM (Local).
'    Converted '05/01/2009 01:30:42 PM -05:00' to 5/1/2009 6:30:42 PM (Utc).
'    Converted '2008-06-11T16:11:20.0904778Z' to 6/11/2008 9:11:20 AM (Local).
'    Converted '2008-06-11T16:11:20.0904778Z' to 6/11/2008 4:11:20 PM (Utc).

備註

DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime)方法會剖析日期的字串表示，其格式必須是參數所定義的格式 format 。The DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) method parses the string representation of a date, which must be in the format defined by the format parameter. 它類似于 DateTime.ParseExact(String, String, IFormatProvider, DateTimeStyles) 方法，不同之處在于 TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) 如果轉換失敗，方法不會擲回例外狀況。It is similar to the DateTime.ParseExact(String, String, IFormatProvider, DateTimeStyles) method, except that the TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) method does not throw an exception if the conversion fails.

s參數包含要剖析的日期和時間，而且必須使用參數所定義的格式 format 。The s parameter contains the date and time to parse and must be in a format defined by the format parameter. 如果日期、時間和時區元素存在於中 s ，則它們也必須以指定的順序出現 format 。If date, time, and time zone elements are present in s, they must also appear in the order specified by format. 如果 format 定義的日期沒有時間元素，而且剖析作業成功，則產生的 DateTime 值會是午夜 (00:00:00) 。If format defines a date with no time element and the parse operation succeeds, the resulting DateTime value has a time of midnight (00:00:00). 如果 format 定義的時間沒有日期專案，而且剖析作業成功，則產生的 DateTime 值預設為的日期 DateTime.Now.Date ，或具有的日期（ DateTime.MinValue.Date 如果 styles 包含 DateTimeStyles.NoCurrentDateDefault 旗標）。If format defines a time with no date element and the parse operation succeeds, the resulting DateTime value by default has a date of DateTime.Now.Date, or it has a date of DateTime.MinValue.Date if styles includes the DateTimeStyles.NoCurrentDateDefault flag. style參數會決定參數是否 s 可以包含前置、內部或尾端空白字元。The style parameter determines whether the s parameter can contain leading, inner, or trailing white space characters.

如果 s 不包含時區資訊，則 Kind 傳回之物件的屬性 DateTime 為 DateTimeKind.Unspecified 。If s contains no time zone information, the Kind property of the returned DateTime object is DateTimeKind.Unspecified. 您可以使用旗標來變更此行為 DateTimeStyles.AssumeLocal ，它會傳回 DateTime Kind 屬性為的值 DateTimeKind.Local ，或使用 DateTimeStyles.AssumeUniversal 和 DateTimeStyles.AdjustToUniversal 旗標來變更 DateTime 其屬性為的值 Kind DateTimeKind.Utc 。This behavior can be changed by using the DateTimeStyles.AssumeLocal flag, which returns a DateTime value whose Kind property is DateTimeKind.Local, or by using the DateTimeStyles.AssumeUniversal and DateTimeStyles.AdjustToUniversal flags, which returns a DateTime value whose Kind property is DateTimeKind.Utc. 如果包含時區資訊，則會在必要時將時間轉換為當地時間，而傳回之 Kind 物件的屬性 DateTime 會設定為 DateTimeKind.Local 。If s contains time zone information, the time is converted to local time, if necessary, and the Kind property of the returned DateTime object is set to DateTimeKind.Local. 您可以使用旗標來變更此行為， DateTimeStyles.RoundtripKind 以將國際標準時間 (UTC) 轉換為本地時間，並將 Kind 屬性設定為 DateTimeKind.Utc 。This behavior can be changed by using the DateTimeStyles.RoundtripKind flag to not convert Coordinated Universal Time (UTC) to a local time and set the Kind property to DateTimeKind.Utc.

format參數包含對應至參數預期格式的模式 s 。The format parameter contains a pattern that corresponds to the expected format of the s parameter. 參數中的模式是 format 由 自訂日期和時間格式字串 資料表中的一或多個自訂格式規範所組成，或是從 標準日期和時間格式字串 資料表識別預先定義模式的單一標準格式規範。The pattern in the format parameter consists of one or more custom format specifiers from the Custom Date and Time Format Strings table, or a single standard format specifier, which identifies a predefined pattern, from the Standard Date and Time Format Strings table.

如果您未在自訂格式模式中使用日期或時間分隔符號，請針對參數使用不因文化特性而異的文化特性， provider 並使用每個自訂格式規範的最寬形式。If you do not use date or time separators in a custom format pattern, use the invariant culture for the provider parameter and the widest form of each custom format specifier. 例如，如果您想要指定模式中的時數，請指定較寬的表單 "HH"，而不是較窄的格式 "H"。For example, if you want to specify hours in the pattern, specify the wider form, "HH", instead of the narrower form, "H".

特定的日期和時間符號和字串 (例如，特定語言) 中所使用之特定語言的星期幾名稱 s 是由參數所定義 provider ， s 如果 format 是標準格式規範字符串，則為的精確格式。The particular date and time symbols and strings (such as the names of the days of the week in a particular language) used in s are defined by the provider parameter, as is the precise format of s if format is a standard format specifier string. provider參數可以是下列任何一項：The provider parameter can be any of the following:

• CultureInfo物件，表示用來解讀的文化特性 s 。A CultureInfo object that represents the culture used to interpret s. DateTimeFormatInfo由屬性傳回的物件會 DateTimeFormat 定義中的符號和格式 s 。The DateTimeFormatInfo object returned by its DateTimeFormat property defines the symbols and formatting in s.

• DateTimeFormatInfo定義日期和時間資料格式的物件。A DateTimeFormatInfo object that defines the format of date and time data.

• 自訂的 IFormatProvider 執行，其 GetFormat 方法會傳回 CultureInfo DateTimeFormatInfo 提供格式資訊的物件或物件。A custom IFormatProvider implementation whose GetFormat method returns either the CultureInfo object or the DateTimeFormatInfo object that provides formatting information.

如果 provider 為 null ，則 CultureInfo 會使用對應至目前文化特性的物件。If provider is null, the CultureInfo object that corresponds to the current culture is used.

styles參數包含列舉的一或多個成員 DateTimeStyles ，可判斷未定義的空白字元是否 format 可以出現在中，以及如何 s 控制剖析作業的精確行為。The styles parameter includes one or more members of the DateTimeStyles enumeration that determine whether and where white space not defined by format can appear in s and that control the precise behavior of the parse operation. 下表描述列舉的每個成員如何 DateTimeStyles 影響方法的操作 TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) 。The following table describes how each member of the DateTimeStyles enumeration affects the operation of the TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) method.

DateTimeStyles 成員DateTimeStyles member	描述Description
AdjustToUniversal	剖析 s 並視需要將它轉換為 UTC。Parses s and, if necessary, converts it to UTC. 如果包含 s 時區位移，或 s 不包含任何時區資訊，但包含 styles 旗標 DateTimeStyles.AssumeLocal ，則方法會剖析字串、 ToUniversalTime 將傳回值轉換為 UTC 的呼叫， DateTime 並將 Kind 屬性設定為 DateTimeKind.Utc 。If s includes a time zone offset, or if s contains no time zone information but styles includes the DateTimeStyles.AssumeLocal flag, the method parses the string, calls ToUniversalTime to convert the returned DateTime value to UTC, and sets the Kind property to DateTimeKind.Utc. 如果 s 表示它代表 UTC，或不 s 包含時區資訊，但 styles 包含 DateTimeStyles.AssumeUniversal 旗標，則方法會剖析字串，並不會在傳回的值上執行時區轉換， DateTime 並將屬性設定 Kind 為 DateTimeKind.Utc 。If s indicates that it represents UTC, or if s does not contain time zone information but styles includes the DateTimeStyles.AssumeUniversal flag, the method parses the string, performs no time zone conversion on the returned DateTime value, and sets the Kind property to DateTimeKind.Utc. 在其他所有情況下，旗標沒有任何作用。In all other cases, the flag has no effect.
AllowInnerWhite	指定 format 任何個別的日期或時間專案之間都不能出現未定義的空白字元。Specifies that white space not defined by format can appear between any individual date or time element.
AllowLeadingWhite	指定未定義的空白字元 format 可以出現在的開頭 s 。Specifies that white space not defined by format can appear at the beginning of s.
AllowTrailingWhite	指定未定義的空白字元 format 可以出現在結尾 s 。Specifies that white space not defined by format can appear at the end of s.
AllowWhiteSpaces	指定 s 可能包含不是由定義的前置、內部和尾端空白字元 format 。Specifies that s may contain leading, inner, and trailing white spaces not defined by format.
AssumeLocal	指定如果 s 缺少任何時區資訊，則會假設為代表本地時間。Specifies that if s lacks any time zone information, it is assumed to represent a local time. 除非 DateTimeStyles.AdjustToUniversal 有旗標，否則 Kind 傳回值的屬性 DateTime 會設定為 DateTimeKind.Local 。Unless the DateTimeStyles.AdjustToUniversal flag is present, the Kind property of the returned DateTime value is set to DateTimeKind.Local.
AssumeUniversal	指定如果 s 缺少任何時區資訊，則會假設為代表 UTC。Specifies that if s lacks any time zone information, it is assumed to represent UTC. 除非 DateTimeStyles.AdjustToUniversal 有旗標，否則方法會將傳回的 DateTime 值從 UTC 轉換為當地時間，並將其 Kind 屬性設定為 DateTimeKind.Local 。Unless the DateTimeStyles.AdjustToUniversal flag is present, the method converts the returned DateTime value from UTC to local time and sets its Kind property to DateTimeKind.Local.
NoCurrentDateDefault	如果 s 包含沒有日期資訊的時間，則傳回值的日期會設為 DateTime.MinValue.Date 。If s contains time without date information, the date of the return value is set to DateTime.MinValue.Date.
None	s參數會使用預設值進行剖析。The s parameter is parsed using default values. 不允許出現在中的空白字元 format 。No white space other than that present in format is allowed. 如果 s 缺少日期元件，則傳回值的日期 DateTime 會設為1/1/0001。If s lacks a date component, the date of the returned DateTime value is set to 1/1/0001. 如果 s 不包含時區資訊， Kind 則傳回之物件的屬性 DateTime 會設定為 DateTimeKind.Unspecified 。If s contains no time zone information, the Kind property of the returned DateTime object is set to DateTimeKind.Unspecified. 如果中有時區資訊 s ，時間會轉換為本地時間，而 Kind 傳回之物件的屬性 DateTime 會設定為 DateTimeKind.Local 。If time zone information is present in s, the time is converted to local time and the Kind property of the returned DateTime object is set to DateTimeKind.Local.
RoundtripKind	如果是包含時區資訊的字串，則會嘗試防止轉換成 DateTime 值，並 Kind 將其屬性設定為 DateTimeKind.Local 。For strings that contain time zone information, tries to prevent the conversion to a DateTime value with its Kind property set to DateTimeKind.Local. 此旗標主要會防止 UTC 時間轉換為當地時間。This flag primarily prevents the conversion of UTC times to local times.

給呼叫者的注意事項

在中 .NET Framework 4.NET Framework 4 ， TryParseExact false 如果要剖析的字串包含小時元件和不在協定中的 AM/PM 指示項，方法會傳回。In the .NET Framework 4.NET Framework 4, the TryParseExact method returns false if the string to be parsed contains an hour component and an AM/PM designator that are not in agreement. 在 .NET Framework 3.5.NET Framework 3.5 和較早的版本中，會忽略 AM/PM 指示項。In the .NET Framework 3.5.NET Framework 3.5 and earlier versions, the AM/PM designator is ignored.

另請參閱

• ParseExact
• CultureInfo
• DateTimeFormatInfo
• 在 .NET Framework 中剖析日期和時間字串Parsing Date and Time Strings in the .NET Framework
• 標準日期和時間格式字串Standard Date and Time Format Strings
• 自訂日期和時間格式字串Custom Date and Time Format Strings

public:
 static bool TryParseExact(System::String ^ s, cli::array <System::String ^> ^ formats, IFormatProvider ^ provider, System::Globalization::DateTimeStyles style, [Runtime::InteropServices::Out] DateTime % result);

public static bool TryParseExact (string s, string[] formats, IFormatProvider provider, System.Globalization.DateTimeStyles style, out DateTime result);

static member TryParseExact : string * string[] * IFormatProvider * System.Globalization.DateTimeStyles * DateTime -> bool

Public Shared Function TryParseExact (s As String, formats As String(), provider As IFormatProvider, style As DateTimeStyles, ByRef result As DateTime) As Boolean

參數

傳回

Boolean

如果 true 參數轉換成功，則為 s，否則為 false。true if the s parameter was converted successfully; otherwise, false.

例外狀況

範例

下列範例會使用 DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) 方法，以確保可以成功剖析許多可能格式的字串。The following example uses the DateTime.TryParseExact(String, String, IFormatProvider, DateTimeStyles, DateTime) method to ensure that a string in a number of possible formats can be successfully parsed .

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      string[] formats= {"M/d/yyyy h:mm:ss tt", "M/d/yyyy h:mm tt",
                         "MM/dd/yyyy hh:mm:ss", "M/d/yyyy h:mm:ss",
                         "M/d/yyyy hh:mm tt", "M/d/yyyy hh tt",
                         "M/d/yyyy h:mm", "M/d/yyyy h:mm",
                         "MM/dd/yyyy hh:mm", "M/dd/yyyy hh:mm"};
      string[] dateStrings = {"5/1/2009 6:32 PM", "05/01/2009 6:32:05 PM",
                              "5/1/2009 6:32:00", "05/01/2009 06:32",
                              "05/01/2009 06:32:00 PM", "05/01/2009 06:32:00"};
      DateTime dateValue;

      foreach (string dateString in dateStrings)
      {
         if (DateTime.TryParseExact(dateString, formats,
                                    new CultureInfo("en-US"),
                                    DateTimeStyles.None,
                                    out dateValue))
            Console.WriteLine("Converted '{0}' to {1}.", dateString, dateValue);
         else
            Console.WriteLine("Unable to convert '{0}' to a date.", dateString);
      }
   }
}
// The example displays the following output:
//       Converted '5/1/2009 6:32 PM' to 5/1/2009 6:32:00 PM.
//       Converted '05/01/2009 6:32:05 PM' to 5/1/2009 6:32:05 PM.
//       Converted '5/1/2009 6:32:00' to 5/1/2009 6:32:00 AM.
//       Converted '05/01/2009 06:32' to 5/1/2009 6:32:00 AM.
//       Converted '05/01/2009 06:32:00 PM' to 5/1/2009 6:32:00 PM.
//       Converted '05/01/2009 06:32:00' to 5/1/2009 6:32:00 AM.

Imports System.Globalization

Public Module Example
   Public Sub Main()
      Dim formats() As String = {"M/d/yyyy h:mm:ss tt", "M/d/yyyy h:mm tt", _
                                 "MM/dd/yyyy hh:mm:ss", "M/d/yyyy h:mm:ss", _
                                 "M/d/yyyy hh:mm tt", "M/d/yyyy hh tt", _
                                 "M/d/yyyy h:mm", "M/d/yyyy h:mm", _
                                 "MM/dd/yyyy hh:mm", "M/dd/yyyy hh:mm"}
      Dim dateStrings() As String = {"5/1/2009 6:32 PM", "05/01/2009 6:32:05 PM", _
                                     "5/1/2009 6:32:00", "05/01/2009 06:32", _
                                     "05/01/2009 06:32:00 PM", "05/01/2009 06:32:00"} 

      Dim dateValue As DateTime
      
      For Each dateString As String In dateStrings
         If Date.TryParseExact(dateString, formats, _
                               New CultureInfo("en-US"), _
                               DateTimeStyles.None, _
                               dateValue) Then
            Console.WriteLine("Converted '{0}' to {1}.", dateString, dateValue)
         Else
            Console.WriteLine("Unable to convert '{0}' to a date.", dateString)
         End If                                               
      Next
   End Sub   
End Module
' The example displays the following output:
'       Converted '5/1/2009 6:32 PM' to 5/1/2009 6:32:00 PM.
'       Converted '05/01/2009 6:32:05 PM' to 5/1/2009 6:32:05 PM.
'       Converted '5/1/2009 6:32:00' to 5/1/2009 6:32:00 AM.
'       Converted '05/01/2009 06:32' to 5/1/2009 6:32:00 AM.
'       Converted '05/01/2009 06:32:00 PM' to 5/1/2009 6:32:00 PM.
'       Converted '05/01/2009 06:32:00' to 5/1/2009 6:32:00 AM.

備註

DateTime.TryParseExact(String, String[], IFormatProvider, DateTimeStyles, DateTime)方法會剖析日期的字串表示，該日期符合指派給參數的任何一個模式 formats 。The DateTime.TryParseExact(String, String[], IFormatProvider, DateTimeStyles, DateTime) method parses the string representation of a date that matches any one of the patterns assigned to the formats parameter. 它類似于 DateTime.ParseExact(String, String[], IFormatProvider, DateTimeStyles) 方法，但 TryParseExact 如果轉換失敗，方法不會擲回例外狀況。It is like the DateTime.ParseExact(String, String[], IFormatProvider, DateTimeStyles) method, except the TryParseExact method does not throw an exception if the conversion fails.

s參數包含要剖析的日期和時間。The s parameter contains the date and time to parse. 如果 s 參數只包含時間且沒有日期，除非參數包含旗標，否則會使用目前的日期， style 在此 DateTimeStyles.NoCurrentDateDefault 情況下，會使用預設的日期 (DateTime.Date.MinValue) 。If the s parameter contains only a time and no date, the current date is used unless the style parameter includes the DateTimeStyles.NoCurrentDateDefault flag, in which case the default date (DateTime.Date.MinValue) is used. 如果 s 參數只包含日期而沒有時間，則會使用午夜 (00:00:00) 。If the s parameter contains only a date and no time, midnight (00:00:00) is used. style參數也會判斷參數是否 s 可以包含前置、內部或尾端空白字元，而不是中的其中一個格式字串所允許的空白字元 formats 。The style parameter also determines whether the s parameter can contain leading, inner, or trailing white space characters other than those permitted by one of the format strings in formats.

如果 s 不包含時區資訊，則 Kind 傳回之物件的屬性 DateTime 為 DateTimeKind.Unspecified 。If s contains no time zone information, the Kind property of the returned DateTime object is DateTimeKind.Unspecified. 您可以使用旗標來變更此行為 DateTimeStyles.AssumeLocal ，它會傳回 DateTime Kind 屬性為的值 DateTimeKind.Local ，或使用 DateTimeStyles.AssumeUniversal 和 DateTimeStyles.AdjustToUniversal 旗標來變更 DateTime 其屬性為的值 Kind DateTimeKind.Utc 。This behavior can be changed by using the DateTimeStyles.AssumeLocal flag, which returns a DateTime value whose Kind property is DateTimeKind.Local, or by using the DateTimeStyles.AssumeUniversal and DateTimeStyles.AdjustToUniversal flags, which returns a DateTime value whose Kind property is DateTimeKind.Utc. 如果包含時區資訊，則會在必要時將時間轉換為當地時間，而傳回之 Kind 物件的屬性 DateTime 會設定為 DateTimeKind.Local 。If s contains time zone information, the time is converted to local time, if necessary, and the Kind property of the returned DateTime object is set to DateTimeKind.Local. 您可以使用旗標來變更此行為， DateTimeStyles.RoundtripKind 以將國際標準時間 (UTC) 轉換為本地時間，並將 Kind 屬性設定為 DateTimeKind.Utc 。This behavior can be changed by using the DateTimeStyles.RoundtripKind flag to not convert Coordinated Universal Time (UTC) to a local time and set the Kind property to DateTimeKind.Utc.

formats參數包含模式的陣列，如果剖析作業成功，則其中一個 s 必須完全相符。The formats parameter contains an array of patterns, one of which s must match exactly if the parse operation is to succeed. 參數中的模式 formats 包含 自訂日期和時間格式字串 資料表中的一或多個自訂格式規範，或從 標準日期和時間格式字串 資料表識別預先定義模式的單一標準格式規範。The patterns in the formats parameter consist of one or more custom format specifiers from the Custom Date and Time Format Strings table, or a single standard format specifier, which identifies a predefined pattern, from the Standard Date and Time Format Strings table.

如果您未在自訂格式模式中使用日期或時間分隔符號，請針對參數使用不因文化特性而異的文化特性， provider 並使用每個自訂格式規範的最寬形式。If you do not use date or time separators in a custom format pattern, use the invariant culture for the provider parameter and the widest form of each custom format specifier. 例如，如果您想要指定模式中的時數，請指定較寬的表單 "HH"，而不是較窄的格式 "H"。For example, if you want to specify hours in the pattern, specify the wider form, "HH", instead of the narrower form, "H".

特定的日期和時間符號和字串 (例如，特定語言) 中所使用之特定語言的星期幾名稱 s 是由參數所定義 provider ， s 如果 format 是標準格式規範字符串，則為的精確格式。The particular date and time symbols and strings (such as the names of the days of the week in a particular language) used in s are defined by the provider parameter, as is the precise format of s if format is a standard format specifier string. provider參數可以是下列任何一項：The provider parameter can be any of the following:

• CultureInfo物件，表示用來解讀的文化特性 s 。A CultureInfo object that represents the culture used to interpret s. DateTimeFormatInfo由屬性傳回的物件會 DateTimeFormat 定義中的符號和格式 s 。The DateTimeFormatInfo object returned by its DateTimeFormat property defines the symbols and formatting in s.

• DateTimeFormatInfo定義日期和時間資料格式的物件。A DateTimeFormatInfo object that defines the format of date and time data.

• 自訂的 IFormatProvider 執行，其 GetFormat 方法會傳回 CultureInfo DateTimeFormatInfo 提供格式資訊的物件或物件。A custom IFormatProvider implementation whose GetFormat method returns either the CultureInfo object or the DateTimeFormatInfo object that provides formatting information.

如果 provider 為 null ，則 CultureInfo 會使用對應至目前文化特性的物件。If provider is null, the CultureInfo object that corresponds to the current culture is used.

styles參數包含列舉的一或多個成員 DateTimeStyles ，可判斷未定義的空白字元是否 format 可以出現在中，以及如何 s 控制剖析作業的精確行為。The styles parameter includes one or more members of the DateTimeStyles enumeration that determine whether and where white space not defined by format can appear in s and that control the precise behavior of the parse operation. 下表描述列舉的每個成員如何 DateTimeStyles 影響方法的操作 TryParseExact(String, String[], IFormatProvider, DateTimeStyles, DateTime) 。The following table describes how each member of the DateTimeStyles enumeration affects the operation of the TryParseExact(String, String[], IFormatProvider, DateTimeStyles, DateTime) method.

DateTimeStyles 成員DateTimeStyles member	描述Description
AdjustToUniversal	剖析 s 並視需要將它轉換為 UTC。Parses s and, if necessary, converts it to UTC. 如果包含 s 時區位移，或 s 不包含任何時區資訊，但包含 styles 旗標 DateTimeStyles.AssumeLocal ，則方法會剖析字串、 ToUniversalTime 將傳回值轉換為 UTC 的呼叫， DateTime 並將 Kind 屬性設定為 DateTimeKind.Utc 。If s includes a time zone offset, or if s contains no time zone information but styles includes the DateTimeStyles.AssumeLocal flag, the method parses the string, calls ToUniversalTime to convert the returned DateTime value to UTC, and sets the Kind property to DateTimeKind.Utc. 如果 s 表示它代表 UTC，或不 s 包含時區資訊，但 styles 包含 DateTimeStyles.AssumeUniversal 旗標，則方法會剖析字串，並不會在傳回的值上執行時區轉換， DateTime 並將屬性設定 Kind 為 DateTimeKind.Utc 。If s indicates that it represents UTC, or if s does not contain time zone information but styles includes the DateTimeStyles.AssumeUniversal flag, the method parses the string, performs no time zone conversion on the returned DateTime value, and sets the Kind property to DateTimeKind.Utc. 在其他所有情況下，旗標沒有任何作用。In all other cases, the flag has no effect.
AllowInnerWhite	指定 format 任何個別的日期或時間專案之間都不能出現未定義的空白字元。Specifies that white space not defined by format can appear between any individual date or time element.
AllowLeadingWhite	指定未定義的空白字元 format 可以出現在的開頭 s 。Specifies that white space not defined by format can appear at the beginning of s.
AllowTrailingWhite	指定未定義的空白字元 format 可以出現在結尾 s 。Specifies that white space not defined by format can appear at the end of s.
AllowWhiteSpaces	指定 s 可能包含不是由定義的前置、內部和尾端空白字元 format 。Specifies that s may contain leading, inner, and trailing white spaces not defined by format.
AssumeLocal	指定如果 s 缺少任何時區資訊，則會假設為代表本地時間。Specifies that if s lacks any time zone information, it is assumed to represent a local time. 除非 DateTimeStyles.AdjustToUniversal 有旗標，否則 Kind 傳回值的屬性 DateTime 會設定為 DateTimeKind.Local 。Unless the DateTimeStyles.AdjustToUniversal flag is present, the Kind property of the returned DateTime value is set to DateTimeKind.Local.
AssumeUniversal	指定如果 s 缺少任何時區資訊，則會假設為代表 UTC。Specifies that if s lacks any time zone information, it is assumed to represent UTC. 除非 DateTimeStyles.AdjustToUniversal 有旗標，否則方法會將傳回的 DateTime 值從 UTC 轉換為當地時間，並將其 Kind 屬性設定為 DateTimeKind.Local 。Unless the DateTimeStyles.AdjustToUniversal flag is present, the method converts the returned DateTime value from UTC to local time and sets its Kind property to DateTimeKind.Local.
NoCurrentDateDefault	如果 s 包含沒有日期資訊的時間，則傳回值的日期會設為 DateTime.MinValue.Date 。If s contains time without date information, the date of the return value is set to DateTime.MinValue.Date.
None	s參數會使用預設值進行剖析。The s parameter is parsed using default values. 不允許出現在中的空白字元 format 。No white space other than that present in format is allowed. 如果 s 缺少日期元件，則傳回值的日期 DateTime 會設為1/1/0001。If s lacks a date component, the date of the returned DateTime value is set to 1/1/0001. 如果 s 不包含時區資訊， Kind 則傳回之物件的屬性 DateTime 會設定為 DateTimeKind.Unspecified 。If s contains no time zone information, the Kind property of the returned DateTime object is set to DateTimeKind.Unspecified. 如果中有時區資訊 s ，時間會轉換為本地時間，而 Kind 傳回之物件的屬性 DateTime 會設定為 DateTimeKind.Local 。If time zone information is present in s, the time is converted to local time and the Kind property of the returned DateTime object is set to DateTimeKind.Local.
RoundtripKind	如果是包含時區資訊的字串，則會嘗試防止轉換成 DateTime 值，並 Kind 將其屬性設定為 DateTimeKind.Local 。For strings that contain time zone information, tries to prevent the conversion to a DateTime value with its Kind property set to DateTimeKind.Local. 此旗標主要會防止 UTC 時間轉換為當地時間。This flag primarily prevents the conversion of UTC times to local times.

給呼叫者的注意事項

在中 .NET Framework 4.NET Framework 4 ， TryParseExact false 如果要剖析的字串包含小時元件和不在協定中的 AM/PM 指示項，方法會傳回。In the .NET Framework 4.NET Framework 4, the TryParseExact method returns false if the string to be parsed contains an hour component and an AM/PM designator that are not in agreement. 在 .NET Framework 3.5.NET Framework 3.5 和較早的版本中，會忽略 AM/PM 指示項。In the .NET Framework 3.5.NET Framework 3.5 and earlier versions, the AM/PM designator is ignored.

另請參閱

• ParseExact
• CultureInfo
• DateTimeFormatInfo
• 在 .NET Framework 中剖析日期和時間字串Parsing Date and Time Strings in the .NET Framework
• 標準日期和時間格式字串Standard Date and Time Format Strings
• 自訂日期和時間格式字串Custom Date and Time Format Strings