CompareInfo.IsPrefix 方法

参考

定义

命名空间:: System.Globalization

程序集:: System.Globalization.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

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确定字符串是否以指定的前缀开头。

重载

IsPrefix(String, String)	确定指定的源字符串是否以指定的前缀开头。
IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions)	确定某一字符只读范围是否以指定前缀开头。
IsPrefix(String, String, CompareOptions)	使用指定的 CompareOptions 值确定指定的源字符串是否以指定的前缀开头。
IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions, Int32)	确定字符串是否以指定的前缀开头。

IsPrefix(String, String)

Source:: CompareInfo.cs

Source:: CompareInfo.cs

Source:: CompareInfo.cs

确定指定的源字符串是否以指定的前缀开头。

public:
 virtual bool IsPrefix(System::String ^ source, System::String ^ prefix);

public:
 bool IsPrefix(System::String ^ source, System::String ^ prefix);

public virtual bool IsPrefix (string source, string prefix);

public bool IsPrefix (string source, string prefix);

abstract member IsPrefix : string * string -> bool
override this.IsPrefix : string * string -> bool

member this.IsPrefix : string * string -> bool

Public Overridable Function IsPrefix (source As String, prefix As String) As Boolean

Public Function IsPrefix (source As String, prefix As String) As Boolean

参数

source: String

要在其中搜索的字符串。

prefix: String

要与 source 的开头进行比较的字符串。

Boolean

如果 prefix 的长度小于或等于 source 的长度，并且 source 以 prefix 开始，则为 true；否则为 false。

例外

ArgumentNullException

source 为 null。

- 或 -

prefix 为 null。

示例

以下示例确定字符串是另一个字符串的前缀还是后缀。

using namespace System;
using namespace System::Globalization;
int main()
{
   
   // Defines the strings to compare.
   String^ myStr1 = "calle";
   String^ myStr2 = "llegar";
   String^ myXfix = "lle";
   
   // Uses the CompareInfo property of the InvariantCulture.
   CompareInfo^ myComp = CultureInfo::InvariantCulture->CompareInfo;
   
   // Determines whether myXfix is a prefix of S"calle" and S"llegar".
   Console::WriteLine( "IsPrefix( {0}, {1}) : {2}", myStr1, myXfix, myComp->IsPrefix( myStr1, myXfix ) );
   Console::WriteLine( "IsPrefix( {0}, {1}) : {2}", myStr2, myXfix, myComp->IsPrefix( myStr2, myXfix ) );
   
   // Determines whether myXfix is a suffix of S"calle" and S"llegar".
   Console::WriteLine( "IsSuffix( {0}, {1}) : {2}", myStr1, myXfix, myComp->IsSuffix( myStr1, myXfix ) );
   Console::WriteLine( "IsSuffix( {0}, {1}) : {2}", myStr2, myXfix, myComp->IsSuffix( myStr2, myXfix ) );
}

/*
This code produces the following output.

IsPrefix(calle, lle) : False
IsPrefix(llegar, lle) : True
IsSuffix(calle, lle) : True
IsSuffix(llegar, lle) : False

*/

using System;
using System.Globalization;

public class SamplesCompareInfo  {

   public static void Main()  {

      // Defines the strings to compare.
      String myStr1 = "calle";
      String myStr2 = "llegar";
      String myXfix = "lle";

      // Uses the CompareInfo property of the InvariantCulture.
      CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;

      // Determines whether myXfix is a prefix of "calle" and "llegar".
      Console.WriteLine( "IsPrefix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsPrefix( myStr1, myXfix ) );
      Console.WriteLine( "IsPrefix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsPrefix( myStr2, myXfix ) );

      // Determines whether myXfix is a suffix of "calle" and "llegar".
      Console.WriteLine( "IsSuffix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsSuffix( myStr1, myXfix ) );
      Console.WriteLine( "IsSuffix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsSuffix( myStr2, myXfix ) );
   }
}


/*
This code produces the following output.

IsPrefix( calle, lle ) : False
IsPrefix( llegar, lle ) : True
IsSuffix( calle, lle ) : True
IsSuffix( llegar, lle ) : False

*/

Imports System.Globalization

Public Class SamplesCompareInfo

   Public Shared Sub Main()

      ' Defines the strings to compare.
      Dim myStr1 As [String] = "calle"
      Dim myStr2 As [String] = "llegar"
      Dim myXfix As [String] = "lle"

      ' Uses the CompareInfo property of the InvariantCulture.
      Dim myComp As CompareInfo = CultureInfo.InvariantCulture.CompareInfo

      ' Determines whether myXfix is a prefix of "calle" and "llegar".
      Console.WriteLine("IsPrefix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsPrefix(myStr1, myXfix))
      Console.WriteLine("IsPrefix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsPrefix(myStr2, myXfix))

      ' Determines whether myXfix is a suffix of "calle" and "llegar".
      Console.WriteLine("IsSuffix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsSuffix(myStr1, myXfix))
      Console.WriteLine("IsSuffix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsSuffix(myStr2, myXfix))

   End Sub

End Class


'This code produces the following output.
'
'IsPrefix( calle, lle ) : False
'IsPrefix( llegar, lle ) : True
'IsSuffix( calle, lle ) : True
'IsSuffix( llegar, lle ) : False

注解

每个字符串以空子字符串开头和结尾 (“”) ;因此，如果 prefix 是空字符串，则此方法返回 true。

注意

如果可能，应调用具有类型 CompareOptions 参数的字符串比较方法，以指定预期的比较类型。一般情况下，使用语言选项 (使用当前区域性) 来比较用户界面中显示的字符串，并指定 CompareOptions.Ordinal 或 CompareOptions.OrdinalIgnoreCase 进行安全比较。

另请参阅

IsSuffix(String, String, CompareOptions)

适用于

IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions)

Source:: CompareInfo.cs

Source:: CompareInfo.cs

Source:: CompareInfo.cs

确定某一字符只读范围是否以指定前缀开头。

public bool IsPrefix (ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, System.Globalization.CompareOptions options = System.Globalization.CompareOptions.None);

member this.IsPrefix : ReadOnlySpan<char> * ReadOnlySpan<char> * System.Globalization.CompareOptions -> bool

Public Function IsPrefix (source As ReadOnlySpan(Of Char), prefix As ReadOnlySpan(Of Char), Optional options As CompareOptions = System.Globalization.CompareOptions.None) As Boolean

参数

source: ReadOnlySpan<Char>

要在其中搜索的字符只读范围。

prefix: ReadOnlySpan<Char>

要尝试与 source 开头相匹配的前缀。

options: CompareOptions

要在匹配过程中使用的 CompareOptions 枚举值的可选组合。默认值是 None。

Boolean

如果 prefix 出现在 source 的开头，则为 true；否则为 false。

例外

ArgumentException

options 包含不受支持的标志组合。

适用于

IsPrefix(String, String, CompareOptions)

Source:: CompareInfo.cs

Source:: CompareInfo.cs

Source:: CompareInfo.cs

使用指定的 CompareOptions 值确定指定的源字符串是否以指定的前缀开头。

public:
 virtual bool IsPrefix(System::String ^ source, System::String ^ prefix, System::Globalization::CompareOptions options);

public:
 bool IsPrefix(System::String ^ source, System::String ^ prefix, System::Globalization::CompareOptions options);

public virtual bool IsPrefix (string source, string prefix, System.Globalization.CompareOptions options);

public bool IsPrefix (string source, string prefix, System.Globalization.CompareOptions options);

abstract member IsPrefix : string * string * System.Globalization.CompareOptions -> bool
override this.IsPrefix : string * string * System.Globalization.CompareOptions -> bool

member this.IsPrefix : string * string * System.Globalization.CompareOptions -> bool

Public Overridable Function IsPrefix (source As String, prefix As String, options As CompareOptions) As Boolean

Public Function IsPrefix (source As String, prefix As String, options As CompareOptions) As Boolean

参数

source: String

要在其中搜索的字符串。

prefix: String

要与 source 的开头进行比较的字符串。

options: CompareOptions

一个值，用于定义应如何比较 source 和 prefix。 options 可以为枚举值 Ordinal，或为以下一个或多个值的按位组合：IgnoreCase、IgnoreSymbols、IgnoreNonSpace、IgnoreWidth 和 IgnoreKanaType。

Boolean

如果 prefix 的长度小于或等于 source 的长度，并且 source 以 prefix 开始，则为 true；否则为 false。

例外

ArgumentNullException

source 为 null。

- 或 -

prefix 为 null。

ArgumentException

options 包含无效的 CompareOptions 值。

示例

以下示例使用 CompareOptions确定字符串是另一个字符串的前缀还是后缀。

using namespace System;
using namespace System::Globalization;
int main()
{
   
   // Defines the strings to compare.
   String^ myStr1 = "calle";
   String^ myStr2 = "llegar";
   String^ myXfix = "LLE";
   
   // Uses the CompareInfo property of the InvariantCulture.
   CompareInfo^ myComp = CultureInfo::InvariantCulture->CompareInfo;
   Console::WriteLine( "IsSuffix \"{0}\", \"{1}\"", myStr1, myXfix );
   Console::WriteLine( "   With no CompareOptions            : {0}", myComp->IsSuffix( myStr1, myXfix ) );
   Console::WriteLine( "   With None                         : {0}", myComp->IsSuffix( myStr1, myXfix, CompareOptions::None ) );
   Console::WriteLine( "   With Ordinal                      : {0}", myComp->IsSuffix( myStr1, myXfix, CompareOptions::Ordinal ) );
   Console::WriteLine( "   With IgnoreCase                   : {0}", myComp->IsSuffix( myStr1, myXfix, CompareOptions::IgnoreCase ) );
   Console::WriteLine( "IsPrefix \"{0}\", \"{1}\"", myStr2, myXfix );
   Console::WriteLine( "   With no CompareOptions            : {0}", myComp->IsPrefix( myStr2, myXfix ) );
   Console::WriteLine( "   With None                         : {0}", myComp->IsPrefix( myStr2, myXfix, CompareOptions::None ) );
   Console::WriteLine( "   With Ordinal                      : {0}", myComp->IsPrefix( myStr2, myXfix, CompareOptions::Ordinal ) );
   Console::WriteLine( "   With IgnoreCase                   : {0}", myComp->IsPrefix( myStr2, myXfix, CompareOptions::IgnoreCase ) );
}

/*
This code produces the following output.

IsSuffix "calle", "LLE"
   With no CompareOptions            : False
   With None                         : False
   With Ordinal                      : False
   With IgnoreCase                   : True
IsPrefix "llegar", "LLE"
   With no CompareOptions            : False
   With None                         : False
   With Ordinal                      : False
   With IgnoreCase                   : True
*/

using System;
using System.Globalization;

public class SamplesCompareInfo  {

   public static void Main()  {

      // Defines the strings to compare.
      String myStr1 = "calle";
      String myStr2 = "llegar";
      String myXfix = "LLE";

      // Uses the CompareInfo property of the InvariantCulture.
      CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;

      Console.WriteLine( "IsSuffix \"{0}\", \"{1}\"", myStr1, myXfix );
      Console.WriteLine( "   With no CompareOptions            : {0}", myComp.IsSuffix( myStr1, myXfix ) );
      Console.WriteLine( "   With None                         : {0}", myComp.IsSuffix( myStr1, myXfix, CompareOptions.None ) );
      Console.WriteLine( "   With Ordinal                      : {0}", myComp.IsSuffix( myStr1, myXfix, CompareOptions.Ordinal ) );
      Console.WriteLine( "   With IgnoreCase                   : {0}", myComp.IsSuffix( myStr1, myXfix, CompareOptions.IgnoreCase ) );

      Console.WriteLine( "IsPrefix \"{0}\", \"{1}\"", myStr2, myXfix );
      Console.WriteLine( "   With no CompareOptions            : {0}", myComp.IsPrefix( myStr2, myXfix ) );
      Console.WriteLine( "   With None                         : {0}", myComp.IsPrefix( myStr2, myXfix, CompareOptions.None ) );
      Console.WriteLine( "   With Ordinal                      : {0}", myComp.IsPrefix( myStr2, myXfix, CompareOptions.Ordinal ) );
      Console.WriteLine( "   With IgnoreCase                   : {0}", myComp.IsPrefix( myStr2, myXfix, CompareOptions.IgnoreCase ) );
   }
}


/*
This code produces the following output.

IsSuffix "calle", "LLE"
   With no CompareOptions            : False
   With None                         : False
   With Ordinal                      : False
   With IgnoreCase                   : True
IsPrefix "llegar", "LLE"
   With no CompareOptions            : False
   With None                         : False
   With Ordinal                      : False
   With IgnoreCase                   : True

*/

Imports System.Globalization

Public Class SamplesCompareInfo

   Public Shared Sub Main()

      ' Defines the strings to compare.
      Dim myStr1 As [String] = "calle"
      Dim myStr2 As [String] = "llegar"
      Dim myXfix As [String] = "LLE"

      ' Uses the CompareInfo property of the InvariantCulture.
      Dim myComp As CompareInfo = CultureInfo.InvariantCulture.CompareInfo

      Console.WriteLine("IsSuffix ""{0}"", ""{1}""", myStr1, myXfix)
      Console.WriteLine("   With no CompareOptions            : {0}", myComp.IsSuffix(myStr1, myXfix))
      Console.WriteLine("   With None                         : {0}", myComp.IsSuffix(myStr1, myXfix, CompareOptions.None))
      Console.WriteLine("   With Ordinal                      : {0}", myComp.IsSuffix(myStr1, myXfix, CompareOptions.Ordinal))
      Console.WriteLine("   With IgnoreCase                   : {0}", myComp.IsSuffix(myStr1, myXfix, CompareOptions.IgnoreCase))

      Console.WriteLine("IsPrefix ""{0}"", ""{1}""", myStr2, myXfix)
      Console.WriteLine("   With no CompareOptions            : {0}", myComp.IsPrefix(myStr2, myXfix))
      Console.WriteLine("   With None                         : {0}", myComp.IsPrefix(myStr2, myXfix, CompareOptions.None))
      Console.WriteLine("   With Ordinal                      : {0}", myComp.IsPrefix(myStr2, myXfix, CompareOptions.Ordinal))
      Console.WriteLine("   With IgnoreCase                   : {0}", myComp.IsPrefix(myStr2, myXfix, CompareOptions.IgnoreCase))

   End Sub

End Class


'This code produces the following output.
'
'IsSuffix "calle", "LLE"
'   With no CompareOptions            : False
'   With None                         : False
'   With Ordinal                      : False
'   With IgnoreCase                   : True
'IsPrefix "llegar", "LLE"
'   With no CompareOptions            : False
'   With None                         : False
'   With Ordinal                      : False
'   With IgnoreCase                   : True

注解

每个字符串以空子字符串开头和结尾 (“”) ;因此，如果 prefix 是空字符串，则此方法返回 true。

该值 CompareOptions.StringSort 对此方法无效。

注意

另请参阅

适用于

IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions, Int32)

Source:: CompareInfo.cs

Source:: CompareInfo.cs

Source:: CompareInfo.cs

确定字符串是否以指定的前缀开头。

public:
 bool IsPrefix(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, System::Globalization::CompareOptions options, [Runtime::InteropServices::Out] int % matchLength);

public bool IsPrefix (ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, System.Globalization.CompareOptions options, out int matchLength);

member this.IsPrefix : ReadOnlySpan<char> * ReadOnlySpan<char> * System.Globalization.CompareOptions * int -> bool

Public Function IsPrefix (source As ReadOnlySpan(Of Char), prefix As ReadOnlySpan(Of Char), options As CompareOptions, ByRef matchLength As Integer) As Boolean

参数

source: ReadOnlySpan<Char>

要在其中搜索的字符只读范围。

prefix: ReadOnlySpan<Char>

字符的只读范围，其中包含在 source 开头要尝试匹配的前缀。

options: CompareOptions

要在匹配期间使用的 CompareOptions。

matchLength: Int32

当此方法返回时，包含与所需前缀匹配的 source 的字符数。如果执行了语言比较，则这可能与 prefix 的长度不同。如果前缀不匹配，则设置为 0。

Boolean

如果 prefix 出现在 source 的开头，则为 true；否则为 false。

例外

ArgumentException

options 包含不受支持的标志组合。

注解

与其他不采用matchLength参数的重载相比IsPrefix(String, String, CompareOptions)，此方法的开销更大。仅当需要匹配长度信息时，才调用此重载。

适用于

CompareInfo.IsPrefix 方法

定义

重载

IsPrefix(String, String)

参数

返回

例外

示例

注解

另请参阅

适用于

IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions)

参数

返回

例外

适用于

IsPrefix(String, String, CompareOptions)

参数

返回

例外

示例

注解

另请参阅

适用于

IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions, Int32)

参数

返回

例外

注解

适用于

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