C＃| Char.ConvertToUtf32(String，Int32)方法

此方法用于将字符串指定位置的UTF-16编码字符或代理对的值转换为Unicode代码点。

句法：

public static int ConvertToUtf32 (string s, int index);

参数：

s: A string that contains a character or surrogate pair.
index: The index position of the character or surrogate pair in s.

返回值：此方法返回由index所指定的s参数中的字符或代理对表示的21位Unicode代码点。

例外情况：

• ArgumentNullException：如果s为null。
• ArgumentOutOfRangeException：如果index不在s内。
• 参数异常：如果索引不是s内的位置。
• ArgumentException：如果指定的索引位置包含一个代理对，并且该对中的第一个字符不是有效的高代理，或者该对中的第二个字符不是有效的低代理。

下面的程序说明了Char.ConvertToUtf32(String，Int32)方法的用法：

范例1：

// C# program to demonstrate
// Char.ConvertToUtf32(String, Int32)
// Method
using System;
using System.Globalization;
  
class GFG {
  
// Main Method
public static void Main()
{
    try {
  
        // declaring and initializing int 
        // variable with 21 bit unicode
        int utf = 0xF42;
  
        // getting the value
        // using ConvertFromUtf32()
        string value = Char.ConvertFromUtf32(utf);
  
        // getting unicode point
        // using ConvertToUtf32() method
        int val = Char.ConvertToUtf32(value, 0);
  
        // Display the value
        Console.WriteLine("value is 0x{0:X}", val);
    }
      
    catch (ArgumentOutOfRangeException e) {
  
        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}
}

输出：

value is 0xF42

示例2：对于ArgumentOutOfRangeException

// C# program to demonstrate
// Char.ConvertToUtf32(String, Int32)
// Method
using System;
using System.Globalization;
  
class GFG {
  
// Main Method
public static void Main()
{
    try {
  
        // declaring and initializing int 
        // variable with 21 bit unicode
        int utf = 0x42F;
  
        // getting the value
        // using ConvertFromUtf32()
        string value = Char.ConvertFromUtf32(utf);
  
        // getting unicode point
        // using ConvertToUtf32() method
        Console.WriteLine("index is not a position within s.");
        int val = Char.ConvertToUtf32(value, 0xDFFF);
  
        // Display the value
        Console.WriteLine("value is 0x{0:X}", val);
    }
      
    catch (ArgumentOutOfRangeException e) {
  
        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}
}

输出：

index is not a position within s.
Exception Thrown: System.ArgumentOutOfRangeException

示例3：对于ArgumentNullException

// C# program to demonstrate
// Char.ConvertToUtf32(String, Int32)
// Method
using System;
using System.Globalization;
  
class GFG {
  
    // Main Method
    public static void Main()
    {
        try {
  
            // declaring and initializing 
            // int variablewith 21 bit 
            // unicode int utf = 0x42F;
  
            // getting the value
            // using ConvertFromUtf32()
            string value = null;
  
            // getting unicode point
            // using ConvertToUtf32() method
            Console.WriteLine("string value is null");
            int val = Char.ConvertToUtf32(value, 0);
  
            // Display the value
            Console.WriteLine("value is 0x{0:X}", val);
        }
        catch (ArgumentNullException e) {
  
            Console.Write("Exception Thrown: ");
            Console.Write("{0}", e.GetType(), e.Message);
        }
        catch (ArgumentOutOfRangeException e) {
  
            Console.Write("Exception Thrown: ");
            Console.Write("{0}", e.GetType(), e.Message);
        }
        catch (ArgumentException e) {
  
            Console.Write("Exception Thrown: ");
            Console.Write("{0}", e.GetType(), e.Message);
        }
    }
}

输出：

string value is null
Exception Thrown: System.ArgumentNullException

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.char.converttoutf32?view=netframework-4.7.2#System_Char_ConvertToUtf32_System_String_System_Int32_