CompareInfo.IsPrefix Method
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Determines whether a string starts with a specific prefix.
IsPrefix(String, String) |
Determines whether the specified source string starts with the specified prefix. |
IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions) |
Determines whether a read-only span of characters starts with a specific prefix. |
IsPrefix(String, String, CompareOptions) |
Determines whether the specified source string starts with the specified prefix using the specified CompareOptions value. |
IsPrefix(ReadOnlySpan<Char>, ReadOnlySpan<Char>, CompareOptions, Int32) |
Determines whether a string starts with a specific prefix. |
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
Determines whether the specified source string starts with the specified prefix.
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
Parameters
- source
- String
The string to search in.
- prefix
- String
The string to compare with the beginning of source
.
Returns
true
if the length of prefix
is less than or equal to the length of source
and source
starts with prefix
; otherwise, false
.
Exceptions
Examples
The following example determines whether a string is the prefix or suffix of another string.
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
Remarks
Every string starts and ends with an empty substring (""); therefore, if prefix
is an empty string, this method returns true
.
Megjegyzés
When possible, you should call string comparison methods that have a parameter of type CompareOptions to specify the kind of comparison expected. As a general rule, use linguistic options (using the current culture) for comparing strings displayed in the user interface and specify CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase for security comparisons.
See also
Applies to
.NET 9 és más verziók
Termék | Verziók |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1 |
UWP | 10.0 |
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
Determines whether a read-only span of characters starts with a specific prefix.
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
Parameters
- source
- ReadOnlySpan<Char>
The read-only span of characters to search within.
- prefix
- ReadOnlySpan<Char>
The prefix to attempt to match at the start of source
.
- options
- CompareOptions
An optional combination of CompareOptions enumeration values to use during the match. The default value is None.
Returns
true
if prefix
occurs at the start of source
; otherwise, false
.
Exceptions
options
contains an unsupported combination of flags.
Applies to
.NET 9 és más verziók
Termék | Verziók |
---|---|
.NET | 5, 6, 7, 8, 9 |
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
Determines whether the specified source string starts with the specified prefix using the specified CompareOptions value.
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
Parameters
- source
- String
The string to search in.
- prefix
- String
The string to compare with the beginning of source
.
- options
- CompareOptions
A value that defines how source
and prefix
should be compared. options
is either the enumeration value Ordinal, or a bitwise combination of one or more of the following values: IgnoreCase, IgnoreSymbols, IgnoreNonSpace, IgnoreWidth, and IgnoreKanaType.
Returns
true
if the length of prefix
is less than or equal to the length of source
and source
starts with prefix
; otherwise, false
.
Exceptions
options
contains an invalid CompareOptions value.
Examples
The following example determines whether a string is the prefix or suffix of another string using CompareOptions.
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
Remarks
Every string starts and ends with an empty substring (""); therefore, if prefix
is an empty string, this method returns true
.
The CompareOptions.StringSort value is not valid for this method.
Megjegyzés
When possible, you should call string comparison methods that have a parameter of type CompareOptions to specify the kind of comparison expected. As a general rule, use linguistic options (using the current culture) for comparing strings displayed in the user interface and specify CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase for security comparisons.
See also
Applies to
.NET 9 és más verziók
Termék | Verziók |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1 |
UWP | 10.0 |
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
- Source:
- CompareInfo.cs
Determines whether a string starts with a specific prefix.
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
Parameters
- source
- ReadOnlySpan<Char>
The read-only span of characters to search within.
- prefix
- ReadOnlySpan<Char>
The read-only span of characters containing the prefix to attempt to match at the start of source
.
- options
- CompareOptions
The CompareOptions to use during the match.
- matchLength
- Int32
When this method returns, contains the number of characters of source
that matched the desired prefix. This may be different than the length of prefix
if a linguistic comparison is performed. Set to 0 if the prefix did not match.
Returns
true
if prefix
occurs at the start of source
; otherwise, false
.
Exceptions
options
contains an unsupported combination of flags.
Remarks
This method has greater overhead than other IsPrefix(String, String, CompareOptions) overloads that don't take a matchLength
argument. Call this overload only if you require the match length information.
Applies to
.NET 9 és más verziók
Termék | Verziók |
---|---|
.NET | 5, 6, 7, 8, 9 |
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