Char.GetNumericValue 方法

参考

定义

命名空间:: System

程序集:: System.Runtime.dll

程序集:: netstandard.dll

程序集:: mscorlib.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

将指定的数字 Unicode 字符转换为双精度浮点数。

重载

GetNumericValue(String, Int32)	将指定字符串中位于指定位置的数字 Unicode 字符转换为双精度浮点数。
GetNumericValue(Char)	将指定的数字 Unicode 字符转换为双精度浮点数。

GetNumericValue(String, Int32)

将指定字符串中位于指定位置的数字 Unicode 字符转换为双精度浮点数。

public:
 static double GetNumericValue(System::String ^ s, int index);

public static double GetNumericValue (string s, int index);

static member GetNumericValue : string * int -> double

Public Shared Function GetNumericValue (s As String, index As Integer) As Double

参数

s: String

String。

index: Int32

s 中的字符位置。

Double

如果 index 中位于 s 处的字符表示数字，则为该字符的数值；否则为 -1。

例外

ArgumentNullException

s 上声明的默认值为 null。

ArgumentOutOfRangeException

index 小于零或大于 s 中最后一个位置。

示例

下面的代码示例演示了 GetNumericValue 。

using namespace System;
int main()
{
   String^ str =  "input: 1";
   Console::WriteLine( Char::GetNumericValue( '8' ) ); // Output: "8"
   Console::WriteLine( Char::GetNumericValue( str, 7 ) ); // Output: "1"
}

using System;

public class GetNumericValueSample {
    public static void Main() {
        string str = "input: 1";

        Console.WriteLine(Char.GetNumericValue('8'));		// Output: "8"
        Console.WriteLine(Char.GetNumericValue(str, 7));	// Output: "1"
    }
}

open System

let str = "input: 1"

printfn $"{Char.GetNumericValue '8'}"       // Output: "8"
printfn $"{Char.GetNumericValue(str, 7)}"   // Output: "1"

Module GetNumericValueSample
    Sub Main()
        Dim str As String
        str = "input: 1"

        Console.WriteLine(Char.GetNumericValue("8"c))       ' Output: "8"
        Console.WriteLine(Char.GetNumericValue(str, 7))     ' Output: "1"
    End Sub
End Module

注解

s参数必须是数字值的字符串表示形式。例如，如果中位于处的字符 index s 为 "5"，则返回值为5。但是，如果中位于处的 index 字符 s 是 "z"，则返回值为-1。

字符串中的字符位置从零开始索引。

当且仅当字符是以下类别之一的成员时，它才具有关联的数值 UnicodeCategory ： DecimalDigitNumber 、 LetterNumber 或 OtherNumber 。

如果 Char 位置的对象 index 是有效代理项对中的第一个字符，则该方法将 GetNumericValue(String, Int32) 确定代理项对是否构成数字。例如，爱琴大学编号系统由代码点 U + 10107 到 U + 10133 组成。下面的示例使用 ConvertFromUtf32 方法实例化表示每个爱琴大学数的字符串。如示例中的输出所示， GetNumericValue(String, Int32) 如果向传递了爱琴大学数字的高代理项，则该方法将返回正确的数字值。但是，如果将其传递到低代理项，则它仅考虑隔离中的低代理项，并返回-1。

// Define a UTF32 value for each character in the
// Aegean numbering system.
for (int utf32 = 0x10107; utf32 <= 0x10133; utf32++) {
   string surrogate = Char.ConvertFromUtf32(utf32);
   for (int ctr = 0; ctr < surrogate.Length; ctr++)
      Console.Write("U+{0:X4} at position {1}: {2}     ",
                        Convert.ToUInt16(surrogate[ctr]), ctr,
                        Char.GetNumericValue(surrogate, ctr));

   Console.WriteLine();
}
// The example displays the following output:
//       U+D800 at position 0: 1     U+DD07 at position 1: -1
//       U+D800 at position 0: 2     U+DD08 at position 1: -1
//       U+D800 at position 0: 3     U+DD09 at position 1: -1
//       U+D800 at position 0: 4     U+DD0A at position 1: -1
//       U+D800 at position 0: 5     U+DD0B at position 1: -1
//       U+D800 at position 0: 6     U+DD0C at position 1: -1
//       U+D800 at position 0: 7     U+DD0D at position 1: -1
//       U+D800 at position 0: 8     U+DD0E at position 1: -1
//       U+D800 at position 0: 9     U+DD0F at position 1: -1
//       U+D800 at position 0: 10     U+DD10 at position 1: -1
//       U+D800 at position 0: 20     U+DD11 at position 1: -1
//       U+D800 at position 0: 30     U+DD12 at position 1: -1
//       U+D800 at position 0: 40     U+DD13 at position 1: -1
//       U+D800 at position 0: 50     U+DD14 at position 1: -1
//       U+D800 at position 0: 60     U+DD15 at position 1: -1
//       U+D800 at position 0: 70     U+DD16 at position 1: -1
//       U+D800 at position 0: 80     U+DD17 at position 1: -1
//       U+D800 at position 0: 90     U+DD18 at position 1: -1
//       U+D800 at position 0: 100     U+DD19 at position 1: -1
//       U+D800 at position 0: 200     U+DD1A at position 1: -1
//       U+D800 at position 0: 300     U+DD1B at position 1: -1
//       U+D800 at position 0: 400     U+DD1C at position 1: -1
//       U+D800 at position 0: 500     U+DD1D at position 1: -1
//       U+D800 at position 0: 600     U+DD1E at position 1: -1
//       U+D800 at position 0: 700     U+DD1F at position 1: -1
//       U+D800 at position 0: 800     U+DD20 at position 1: -1
//       U+D800 at position 0: 900     U+DD21 at position 1: -1
//       U+D800 at position 0: 1000     U+DD22 at position 1: -1
//       U+D800 at position 0: 2000     U+DD23 at position 1: -1
//       U+D800 at position 0: 3000     U+DD24 at position 1: -1
//       U+D800 at position 0: 4000     U+DD25 at position 1: -1
//       U+D800 at position 0: 5000     U+DD26 at position 1: -1
//       U+D800 at position 0: 6000     U+DD27 at position 1: -1
//       U+D800 at position 0: 7000     U+DD28 at position 1: -1
//       U+D800 at position 0: 8000     U+DD29 at position 1: -1
//       U+D800 at position 0: 9000     U+DD2A at position 1: -1
//       U+D800 at position 0: 10000     U+DD2B at position 1: -1
//       U+D800 at position 0: 20000     U+DD2C at position 1: -1
//       U+D800 at position 0: 30000     U+DD2D at position 1: -1
//       U+D800 at position 0: 40000     U+DD2E at position 1: -1
//       U+D800 at position 0: 50000     U+DD2F at position 1: -1
//       U+D800 at position 0: 60000     U+DD30 at position 1: -1
//       U+D800 at position 0: 70000     U+DD31 at position 1: -1
//       U+D800 at position 0: 80000     U+DD32 at position 1: -1
//       U+D800 at position 0: 90000     U+DD33 at position 1: -1

// Define a UTF32 value for each character in the
// Aegean numbering system.
for utf32 in 0x10107..0x10133 do
    let surrogate = Char.ConvertFromUtf32 utf32
    for i = 0 to surrogate.Length - 1 do
        printf $"U+{Convert.ToUInt16 surrogate[i]:X4} at position {i}: {Char.GetNumericValue(surrogate, i)}     "
    printfn ""

// The example displays the following output:
//       U+D800 at position 0: 1     U+DD07 at position 1: -1
//       U+D800 at position 0: 2     U+DD08 at position 1: -1
//       U+D800 at position 0: 3     U+DD09 at position 1: -1
//       U+D800 at position 0: 4     U+DD0A at position 1: -1
//       U+D800 at position 0: 5     U+DD0B at position 1: -1
//       U+D800 at position 0: 6     U+DD0C at position 1: -1
//       U+D800 at position 0: 7     U+DD0D at position 1: -1
//       U+D800 at position 0: 8     U+DD0E at position 1: -1
//       U+D800 at position 0: 9     U+DD0F at position 1: -1
//       U+D800 at position 0: 10     U+DD10 at position 1: -1
//       U+D800 at position 0: 20     U+DD11 at position 1: -1
//       U+D800 at position 0: 30     U+DD12 at position 1: -1
//       U+D800 at position 0: 40     U+DD13 at position 1: -1
//       U+D800 at position 0: 50     U+DD14 at position 1: -1
//       U+D800 at position 0: 60     U+DD15 at position 1: -1
//       U+D800 at position 0: 70     U+DD16 at position 1: -1
//       U+D800 at position 0: 80     U+DD17 at position 1: -1
//       U+D800 at position 0: 90     U+DD18 at position 1: -1
//       U+D800 at position 0: 100     U+DD19 at position 1: -1
//       U+D800 at position 0: 200     U+DD1A at position 1: -1
//       U+D800 at position 0: 300     U+DD1B at position 1: -1
//       U+D800 at position 0: 400     U+DD1C at position 1: -1
//       U+D800 at position 0: 500     U+DD1D at position 1: -1
//       U+D800 at position 0: 600     U+DD1E at position 1: -1
//       U+D800 at position 0: 700     U+DD1F at position 1: -1
//       U+D800 at position 0: 800     U+DD20 at position 1: -1
//       U+D800 at position 0: 900     U+DD21 at position 1: -1
//       U+D800 at position 0: 1000     U+DD22 at position 1: -1
//       U+D800 at position 0: 2000     U+DD23 at position 1: -1
//       U+D800 at position 0: 3000     U+DD24 at position 1: -1
//       U+D800 at position 0: 4000     U+DD25 at position 1: -1
//       U+D800 at position 0: 5000     U+DD26 at position 1: -1
//       U+D800 at position 0: 6000     U+DD27 at position 1: -1
//       U+D800 at position 0: 7000     U+DD28 at position 1: -1
//       U+D800 at position 0: 8000     U+DD29 at position 1: -1
//       U+D800 at position 0: 9000     U+DD2A at position 1: -1
//       U+D800 at position 0: 10000     U+DD2B at position 1: -1
//       U+D800 at position 0: 20000     U+DD2C at position 1: -1
//       U+D800 at position 0: 30000     U+DD2D at position 1: -1
//       U+D800 at position 0: 40000     U+DD2E at position 1: -1
//       U+D800 at position 0: 50000     U+DD2F at position 1: -1
//       U+D800 at position 0: 60000     U+DD30 at position 1: -1
//       U+D800 at position 0: 70000     U+DD31 at position 1: -1
//       U+D800 at position 0: 80000     U+DD32 at position 1: -1
//       U+D800 at position 0: 90000     U+DD33 at position 1: -1

' Define a UTF32 value for each character in the 
' Aegean numbering system.
For utf32 As Integer = &h10107 To &h10133
   Dim surrogate As String = Char.ConvertFromUtf32(utf32)
   For ctr As Integer = 0 To surrogate.Length - 1
      Console.Write("U+{0:X4} at position {1}: {2}     ", 
                        Convert.ToUInt16(surrogate(ctr)), ctr,  
                        Char.GetNumericValue(surrogate, ctr))
   Next
   Console.WriteLine()
Next    
' The example displays the following output:
'       U+D800 at position 0: 1     U+DD07 at position 1: -1
'       U+D800 at position 0: 2     U+DD08 at position 1: -1
'       U+D800 at position 0: 3     U+DD09 at position 1: -1
'       U+D800 at position 0: 4     U+DD0A at position 1: -1
'       U+D800 at position 0: 5     U+DD0B at position 1: -1
'       U+D800 at position 0: 6     U+DD0C at position 1: -1
'       U+D800 at position 0: 7     U+DD0D at position 1: -1
'       U+D800 at position 0: 8     U+DD0E at position 1: -1
'       U+D800 at position 0: 9     U+DD0F at position 1: -1
'       U+D800 at position 0: 10     U+DD10 at position 1: -1
'       U+D800 at position 0: 20     U+DD11 at position 1: -1
'       U+D800 at position 0: 30     U+DD12 at position 1: -1
'       U+D800 at position 0: 40     U+DD13 at position 1: -1
'       U+D800 at position 0: 50     U+DD14 at position 1: -1
'       U+D800 at position 0: 60     U+DD15 at position 1: -1
'       U+D800 at position 0: 70     U+DD16 at position 1: -1
'       U+D800 at position 0: 80     U+DD17 at position 1: -1
'       U+D800 at position 0: 90     U+DD18 at position 1: -1
'       U+D800 at position 0: 100     U+DD19 at position 1: -1
'       U+D800 at position 0: 200     U+DD1A at position 1: -1
'       U+D800 at position 0: 300     U+DD1B at position 1: -1
'       U+D800 at position 0: 400     U+DD1C at position 1: -1
'       U+D800 at position 0: 500     U+DD1D at position 1: -1
'       U+D800 at position 0: 600     U+DD1E at position 1: -1
'       U+D800 at position 0: 700     U+DD1F at position 1: -1
'       U+D800 at position 0: 800     U+DD20 at position 1: -1
'       U+D800 at position 0: 900     U+DD21 at position 1: -1
'       U+D800 at position 0: 1000     U+DD22 at position 1: -1
'       U+D800 at position 0: 2000     U+DD23 at position 1: -1
'       U+D800 at position 0: 3000     U+DD24 at position 1: -1
'       U+D800 at position 0: 4000     U+DD25 at position 1: -1
'       U+D800 at position 0: 5000     U+DD26 at position 1: -1
'       U+D800 at position 0: 6000     U+DD27 at position 1: -1
'       U+D800 at position 0: 7000     U+DD28 at position 1: -1
'       U+D800 at position 0: 8000     U+DD29 at position 1: -1
'       U+D800 at position 0: 9000     U+DD2A at position 1: -1
'       U+D800 at position 0: 10000     U+DD2B at position 1: -1
'       U+D800 at position 0: 20000     U+DD2C at position 1: -1
'       U+D800 at position 0: 30000     U+DD2D at position 1: -1
'       U+D800 at position 0: 40000     U+DD2E at position 1: -1
'       U+D800 at position 0: 50000     U+DD2F at position 1: -1
'       U+D800 at position 0: 60000     U+DD30 at position 1: -1
'       U+D800 at position 0: 70000     U+DD31 at position 1: -1
'       U+D800 at position 0: 80000     U+DD32 at position 1: -1
'       U+D800 at position 0: 90000     U+DD33 at position 1: -1

适用于

GetNumericValue(Char)

将指定的数字 Unicode 字符转换为双精度浮点数。

public:
 static double GetNumericValue(char c);

public static double GetNumericValue (char c);

static member GetNumericValue : char -> double

Public Shared Function GetNumericValue (c As Char) As Double

参数

c: Char

要转换的 Unicode 字符。

Double

如果该字符表示数字，则数值为 c；否则为 -1.0。

示例

下面的示例演示了 GetNumericValue 。

using namespace System;
int main()
{
   String^ str =  "input: 1";
   Console::WriteLine( Char::GetNumericValue( '8' ) ); // Output: "8"
   Console::WriteLine( Char::GetNumericValue( str, 7 ) ); // Output: "1"
}

using System;

public class GetNumericValueSample {
    public static void Main() {
        string str = "input: 1";

        Console.WriteLine(Char.GetNumericValue('8'));		// Output: "8"
        Console.WriteLine(Char.GetNumericValue(str, 7));	// Output: "1"
    }
}

open System

let str = "input: 1"

printfn $"{Char.GetNumericValue '8'}"       // Output: "8"
printfn $"{Char.GetNumericValue(str, 7)}"   // Output: "1"

Module GetNumericValueSample
    Sub Main()
        Dim str As String
        str = "input: 1"

        Console.WriteLine(Char.GetNumericValue("8"c))       ' Output: "8"
        Console.WriteLine(Char.GetNumericValue(str, 7))     ' Output: "1"
    End Sub
End Module

注解

c参数必须是 Char 数字值的表示形式。例如，如果 c 为 "5"，则返回值为5。但是，如果 c 为 "z"，则返回值为-1.0。

当且仅当字符是以下类别之一的成员时，它才具有关联的数值 UnicodeCategory ： DecimalDigitNumber 、 LetterNumber 或 OtherNumber 。

GetNumericValue方法假定对应于 c 单个语言字符，并检查是否可以将该字符转换为十进制数字。但 Unicode 标准中的一些数字由两个 Char 构成代理项对的对象表示。例如，爱琴大学编号系统由代码点 U + 10107 到 U + 10133 组成。下面的示例使用 ConvertFromUtf32 方法实例化表示爱琴大学1的字符串。如示例的输出所示， GetNumericValue(Char) 如果传递给此字符的高代理项或低代理项，则方法返回-1。

int utf32 = 0x10107;       // AEGEAN NUMBER ONE
string surrogate = Char.ConvertFromUtf32(utf32);
foreach (var ch in surrogate)
   Console.WriteLine("U+{0:X4}: {1}    ", Convert.ToUInt16(ch),
                                          Char.GetNumericValue(ch));

// The example displays the following output:
//       U+D800: -1
//       U+DD07: -1

let utf32 = 0x10107       // AEGEAN NUMBER ONE
let surrogate = Char.ConvertFromUtf32 utf32
for ch in surrogate do
    printfn $"U+{Convert.ToUInt16 ch:X4}: {Char.GetNumericValue ch}    "

// The example displays the following output:
//       U+D800: -1
//       U+DD07: -1

Dim utf32 As Integer = &h10107       ' AEGEAN NUMBER ONE
Dim surrogate As String = Char.ConvertFromUtf32(utf32)
For Each ch In surrogate
   Console.WriteLine("U+{0:X4}: {1}    ", Convert.ToUInt16(ch), 
                                          Char.GetNumericValue(ch))
Next
' The example displays the following output:
'       U+D800: -1
'       U+DD07: -1

另请参阅

GetNumericValue(Rune)

适用于

通过

Char.GetNumericValue 方法

定义

重载

GetNumericValue(String, Int32)

参数

返回

例外

示例

注解

适用于

GetNumericValue(Char)

参数

返回

示例

注解

另请参阅

适用于

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