String.GetHashCode 方法
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
多載
GetHashCode(ReadOnlySpan<Char>, StringComparison) |
使用指定的規則,傳回所提供唯讀字元範圍的雜湊碼。 |
GetHashCode(StringComparison) |
使用指定規則傳回這個字串的雜湊碼。 |
GetHashCode() |
傳回這個字串的雜湊碼。 |
GetHashCode(ReadOnlySpan<Char>) |
傳回所提供唯讀字元範圍的雜湊碼。 |
GetHashCode(ReadOnlySpan<Char>, StringComparison)
使用指定的規則,傳回所提供唯讀字元範圍的雜湊碼。
public:
static int GetHashCode(ReadOnlySpan<char> value, StringComparison comparisonType);
public static int GetHashCode (ReadOnlySpan<char> value, StringComparison comparisonType);
static member GetHashCode : ReadOnlySpan<char> * StringComparison -> int
Public Shared Function GetHashCode (value As ReadOnlySpan(Of Char), comparisonType As StringComparison) As Integer
參數
- value
- ReadOnlySpan<Char>
唯讀的字元範圍。
- comparisonType
- StringComparison
其中一個列舉值,指定要用於比較的規則。
傳回
32 位元帶正負號的整數雜湊碼。
適用於
GetHashCode(StringComparison)
使用指定規則傳回這個字串的雜湊碼。
public:
int GetHashCode(StringComparison comparisonType);
public int GetHashCode (StringComparison comparisonType);
override this.GetHashCode : StringComparison -> int
Public Function GetHashCode (comparisonType As StringComparison) As Integer
參數
- comparisonType
- StringComparison
其中一個列舉值,指定要用於比較的規則。
傳回
32 位元帶正負號的整數雜湊碼。
適用於
GetHashCode()
傳回這個字串的雜湊碼。
public:
override int GetHashCode();
public override int GetHashCode ();
override this.GetHashCode : unit -> int
Public Overrides Function GetHashCode () As Integer
傳回
32 位元帶正負號的整數雜湊碼。
範例
下列範例示範 GetHashCode 使用各種輸入字串的 方法。
using namespace System;
void DisplayHashCode( String^ Operand )
{
int HashCode = Operand->GetHashCode();
Console::WriteLine( "The hash code for \"{0}\" is: 0x{1:X8}, {1}", Operand, HashCode );
}
int main()
{
DisplayHashCode( "" );
DisplayHashCode( "a" );
DisplayHashCode( "ab" );
DisplayHashCode( "abc" );
DisplayHashCode( "abd" );
DisplayHashCode( "abe" );
DisplayHashCode( "abcdef" );
DisplayHashCode( "abcdeg" );
DisplayHashCode( "abcdeh" );
DisplayHashCode( "abcdei" );
DisplayHashCode( "Abcdeg" );
DisplayHashCode( "Abcdeh" );
DisplayHashCode( "Abcdei" );
}
/*
This example displays output like the following:
The hash code for "" is: 0x2D2816FE, 757602046
The hash code for "a" is: 0xCDCAB7BF, -842352705
The hash code for "ab" is: 0xCDE8B7BF, -840386625
The hash code for "abc" is: 0x2001D81A, 536991770
The hash code for "abd" is: 0xC2A94CB5, -1029092171
The hash code for "abe" is: 0x6550C150, 1699791184
The hash code for "abcdef" is: 0x1762906D, 392335469
The hash code for "abcdeg" is: 0x1763906D, 392401005
The hash code for "abcdeh" is: 0x175C906D, 391942253
The hash code for "abcdei" is: 0x175D906D, 392007789
The hash code for "Abcdeg" is: 0x1763954D, 392402253
The hash code for "Abcdeh" is: 0x175C954D, 391943501
The hash code for "Abcdei" is: 0x175D954D, 392009037
*/
using System;
class GetHashCode
{
public static void Main()
{
DisplayHashCode( "" );
DisplayHashCode( "a" );
DisplayHashCode( "ab" );
DisplayHashCode( "abc" );
DisplayHashCode( "abd" );
DisplayHashCode( "abe" );
DisplayHashCode( "abcdef" );
DisplayHashCode( "abcdeg" );
DisplayHashCode( "abcdeh" );
DisplayHashCode( "abcdei" );
DisplayHashCode( "Abcdeg" );
DisplayHashCode( "Abcdeh" );
DisplayHashCode( "Abcdei" );
}
static void DisplayHashCode( String Operand )
{
int HashCode = Operand.GetHashCode( );
Console.WriteLine("The hash code for \"{0}\" is: 0x{1:X8}, {1}",
Operand, HashCode );
}
}
/*
This example displays output like the following:
The hash code for "" is: 0x2D2816FE, 757602046
The hash code for "a" is: 0xCDCAB7BF, -842352705
The hash code for "ab" is: 0xCDE8B7BF, -840386625
The hash code for "abc" is: 0x2001D81A, 536991770
The hash code for "abd" is: 0xC2A94CB5, -1029092171
The hash code for "abe" is: 0x6550C150, 1699791184
The hash code for "abcdef" is: 0x1762906D, 392335469
The hash code for "abcdeg" is: 0x1763906D, 392401005
The hash code for "abcdeh" is: 0x175C906D, 391942253
The hash code for "abcdei" is: 0x175D906D, 392007789
The hash code for "Abcdeg" is: 0x1763954D, 392402253
The hash code for "Abcdeh" is: 0x175C954D, 391943501
The hash code for "Abcdei" is: 0x175D954D, 392009037
*/
let displayHashCode operand =
let hashCode = operand.GetHashCode()
printfn $"The hash code for \"%s{operand}\" is: 0x{1:X8}, {hashCode}"
displayHashCode ""
displayHashCode "a"
displayHashCode "ab"
displayHashCode "abc"
displayHashCode "abd"
displayHashCode "abe"
displayHashCode "abcdef"
displayHashCode "abcdeg"
displayHashCode "abcdeh"
displayHashCode "abcdei"
displayHashCode "Abcdeg"
displayHashCode "Abcdeh"
displayHashCode "Abcdei"
(*
This example displays output like the following:
The hash code for "" is: 0x2D2816FE, 757602046
The hash code for "a" is: 0xCDCAB7BF, -842352705
The hash code for "ab" is: 0xCDE8B7BF, -840386625
The hash code for "abc" is: 0x2001D81A, 536991770
The hash code for "abd" is: 0xC2A94CB5, -1029092171
The hash code for "abe" is: 0x6550C150, 1699791184
The hash code for "abcdef" is: 0x1762906D, 392335469
The hash code for "abcdeg" is: 0x1763906D, 392401005
The hash code for "abcdeh" is: 0x175C906D, 391942253
The hash code for "abcdei" is: 0x175D906D, 392007789
The hash code for "Abcdeg" is: 0x1763954D, 392402253
The hash code for "Abcdeh" is: 0x175C954D, 391943501
The hash code for "Abcdei" is: 0x175D954D, 392009037
*)
Module GetHashCode
Sub Main()
DisplayHashCode("")
DisplayHashCode("a")
DisplayHashCode("ab")
DisplayHashCode("abc")
DisplayHashCode("abd")
DisplayHashCode("abe")
DisplayHashCode("abcdef")
DisplayHashCode("abcdeg")
DisplayHashCode("abcdeh")
DisplayHashCode("abcdei")
DisplayHashCode("Abcdeg")
DisplayHashCode("Abcdeh")
DisplayHashCode("Abcdei")
End Sub
Sub DisplayHashCode(Operand As String)
Dim HashCode As Integer = Operand.GetHashCode()
Console.WriteLine("The hash code for ""{0}"" is: 0x{1:X8}, {1}",
Operand, HashCode)
End Sub
End Module
' This example displays output like the following:
' The hash code for "" is: 0x2D2816FE, 757602046
' The hash code for "a" is: 0xCDCAB7BF, -842352705
' The hash code for "ab" is: 0xCDE8B7BF, -840386625
' The hash code for "abc" is: 0x2001D81A, 536991770
' The hash code for "abd" is: 0xC2A94CB5, -1029092171
' The hash code for "abe" is: 0x6550C150, 1699791184
' The hash code for "abcdef" is: 0x1762906D, 392335469
' The hash code for "abcdeg" is: 0x1763906D, 392401005
' The hash code for "abcdeh" is: 0x175C906D, 391942253
' The hash code for "abcdei" is: 0x175D906D, 392007789
' The hash code for "Abcdeg" is: 0x1763954D, 392402253
' The hash code for "Abcdeh" is: 0x175C954D, 391943501
' The hash code for "Abcdei" is: 0x175D954D, 392009037
備註
的行為 GetHashCode 取決於其實作,這可能會從一個版本的 Common Language Runtime 變更為另一個版本。 發生此情況的原因,是改善 的 GetHashCode 效能。
重要
如果兩個字串物件相等,此方法會 GetHashCode 傳回相同的值。 不過,每個唯一字串值都沒有唯一的雜湊碼值。 不同的字串可以傳回相同的雜湊碼。
雜湊程式碼本身不保證穩定。 相同字串的雜湊碼在 .NET 實作、.NET 版本之間,以及 .NET 平臺 (不同,例如單一 .NET 版本的 32 位和 64 位) 。 在某些情況下,它們甚至可能會因應用程式域而有所不同。 這表示相同程式的後續兩次執行可能會傳回不同的雜湊碼。
如此一來,雜湊碼不應該用在建立它們的應用程式域之外,不應該使用它們做為集合中的索引鍵欄位,而且不應該保存它們。
最後,如果您需要密碼編譯強式雜湊,請勿使用雜湊程式碼,而不是密碼編譯雜湊函式所傳回的值。 針對密碼編譯雜湊,請使用衍生自 或 System.Security.Cryptography.KeyedHashAlgorithm 類別的 System.Security.Cryptography.HashAlgorithm 類別。
如需雜湊碼的詳細資訊,請參閱 Object.GetHashCode 。
在.NET Framework傳統型應用程式中,您可以使用< UseRandomizedStringHashAlgorithm > 元素,根據每個應用程式域產生唯一的雜湊碼。 這可減少衝突數目,並改善使用雜湊表之插入和查閱的整體效能。 下列範例示範如何使用< UseRandomizedStringHashAlgorithm > 元素。 它會定義類別 DisplayString
,其中包含私用字串常數 , s
其值為 「這是字串」。它也包含一個 ShowStringHashCode
方法,其會顯示字串值及其雜湊碼,以及執行方法的應用程式功能變數名稱稱。
using System;
public class Example
{
public static void Main()
{
// Show hash code in current domain.
DisplayString display = new DisplayString();
display.ShowStringHashCode();
// Create a new app domain and show string hash code.
AppDomain domain = AppDomain.CreateDomain("NewDomain");
var display2 = (DisplayString) domain.CreateInstanceAndUnwrap(typeof(Example).Assembly.FullName,
"DisplayString");
display2.ShowStringHashCode();
}
}
public class DisplayString : MarshalByRefObject
{
private String s = "This is a string.";
public override bool Equals(Object obj)
{
String s2 = obj as String;
if (s2 == null)
return false;
else
return s == s2;
}
public bool Equals(String str)
{
return s == str;
}
public override int GetHashCode()
{
return s.GetHashCode();
}
public override String ToString()
{
return s;
}
public void ShowStringHashCode()
{
Console.WriteLine("String '{0}' in domain '{1}': {2:X8}",
s, AppDomain.CurrentDomain.FriendlyName,
s.GetHashCode());
}
}
open System
type DisplayString() =
inherit MarshalByRefObject()
let s = "This is a string."
override _.Equals(obj) =
match obj with
| :? string as s2 -> s = s2
| _ -> false
member _.Equals(str) =
s = str
override _.GetHashCode() =
s.GetHashCode()
override _.ToString() =
s
member _.ShowStringHashCode() =
printfn $"String '{s}' in domain '{AppDomain.CurrentDomain.FriendlyName}': {s.GetHashCode():X8}"
// Show hash code in current domain.
let display = DisplayString()
display.ShowStringHashCode()
// Create a new app domain and show string hash code.
let domain = AppDomain.CreateDomain "NewDomain"
let display2 = domain.CreateInstanceAndUnwrap(typeof<DisplayString>.Assembly.FullName, "DisplayString") :?> DisplayString
display2.ShowStringHashCode()
Module Example
Public Sub Main()
' Show hash code in current domain.
Dim display As New DisplayString()
display.ShowStringHashCode()
' Create a new app domain and show string hash code.
Dim domain As AppDomain = AppDomain.CreateDomain("NewDomain")
Dim display2 = CType(domain.CreateInstanceAndUnwrap(GetType(Example).Assembly.FullName,
"DisplayString"), DisplayString)
display2.ShowStringHashCode()
End Sub
End Module
Public Class DisplayString : Inherits MarshalByRefObject
Private s As String = "This is a string."
Public Overrides Function Equals(obj As Object) As Boolean
Dim s2 As String = TryCast(obj, String)
If s2 Is Nothing Then
Return False
Else
Return s = s2
End If
End Function
Public Overloads Function Equals(str As String) As Boolean
Return s = str
End Function
Public Overrides Function GetHashCode() As Integer
Return s.GetHashCode()
End Function
Public Overrides Function ToString() As String
Return s
End Function
Public Sub ShowStringHashCode()
Console.WriteLine("String '{0}' in domain '{1}': {2:X8}",
s, AppDomain.CurrentDomain.FriendlyName,
s.GetHashCode())
End Sub
End Class
當您在沒有提供組態檔的情況下執行此範例,它會顯示類似下列的輸出。 請注意,字串的雜湊碼在兩個應用程式定義域中相同。
String 'This is a string.' in domain 'PerDomain.exe': 941BCEAC
String 'This is a string.' in domain 'NewDomain': 941BCEAC
不過,如果您將下列組態檔加入至範例的目錄,然後執行這個範例,相同字串的雜湊碼將會因為應用程式定義域不同而有所不同。
<?xml version ="1.0"?>
<configuration>
<runtime>
<UseRandomizedStringHashAlgorithm enabled="1" />
</runtime>
</configuration>
當組態檔存在時,這個範例會顯示下列輸出:
String 'This is a string.' in domain 'PerDomain.exe': 5435776D
String 'This is a string.' in domain 'NewDomain': 75CC8236
重要
雜湊碼可用來有效率地從雜湊表插入和擷取索引鍵物件。 不過,雜湊碼不會唯一識別字串。 相同的字串具有相同的雜湊碼,但 Common Language Runtime 也可以將相同的雜湊程式碼指派給不同的字串。 此外,雜湊碼可能會因 .NET 版本、平臺在單一版本和應用程式域內而有所不同。 因此,您不應該序列化或保存雜湊碼值,也不應該將它們當做雜湊表或字典中的索引鍵使用。
如需使用雜湊碼和 GetHashCode
方法的其他資訊,請參閱 Object.GetHashCode 。
給呼叫者的注意事項
傳 GetHashCode() 回的值與平臺相關。 它與 32 位和 64 位版本的 .NET Framework 不同。 它也可以在 .NET Framework 和 .NET Core 的版本之間有所差異。
另請參閱
適用於
GetHashCode(ReadOnlySpan<Char>)
傳回所提供唯讀字元範圍的雜湊碼。
public:
static int GetHashCode(ReadOnlySpan<char> value);
public static int GetHashCode (ReadOnlySpan<char> value);
static member GetHashCode : ReadOnlySpan<char> -> int
Public Shared Function GetHashCode (value As ReadOnlySpan(Of Char)) As Integer
參數
- value
- ReadOnlySpan<Char>
唯讀的字元範圍。
傳回
32 位元帶正負號的整數雜湊碼。
適用於
意見反應
https://aka.ms/ContentUserFeedback。
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