此方法用于指示字符串指定位置的Char对象是否为低替代值。
句法：
public static bool IsLowSurrogate (string s, int index);参数：
s: It is a String.
index: It is the character position to evaluate in s.
返回值：如果s参数中指定字符的数值范围从U+DC00到U+DFFF则此方法返回true ，否则返回false 。
例外情况：
- ArgumentNullException：如果s为null。
- ArgumentOutOfRangeException：如果索引不是s内的位置。
下面的程序说明了Char.IsLowSurrogate(String，Int32)方法的用法：
范例1：
// C# program to demonstrate
// Char.IsLowSurrogate(String,
// Int32) Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// calling check() Method
check("1234", 3);
check("Tsunami", 3);
check("psyc0lo", 4);
// declaring and initializing string s1
string s1 = new String(new char[] {'a',
'\uD800', '\uDC00', 'z' });
check(s1, 2);
}
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);
}
}
// Defining check() method
public static void check(string s, int i)
{
// checking condition
// using IsLowSurrogate() Method
bool val = Char.IsLowSurrogate(s, i);
// checking
if (val)
Console.WriteLine("String '{0}' contains Low "
+ "Surrogate value at index {1} ", s, i);
else
Console.WriteLine("String '{0}' does't contain any Low"
+ "Surrogate value at index {1}", s, i);
}
}
输出：
String '1234' does't contain any LowSurrogate value at index 3
String 'Tsunami' does't contain any LowSurrogate value at index 3
String 'psyc0lo' does't contain any LowSurrogate value at index 4
String 'að??z' contains Low Surrogate value at index 2
示例2：对于ArgumentNullException
// C# program to demonstrate
// Char.IsLowSurrogate(String,
// Int32) Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// calling check() Method
check("1234", 3);
check("Tsunami", 3);
check("psyc0lo", 4);
// declaring and initializing string s1
string s1 = new String(new char[] {'a',
'\uD800', '\uDC00', 'z' });
check(s1, 2);
Console.WriteLine("");
Console.WriteLine("s is null");
check(null, 4);
}
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);
}
}
// Defining check() method
public static void check(string s, int i)
{
// checking condition
// using IsLowSurrogate() Method
bool val = Char.IsLowSurrogate(s, i);
// checking
if (val)
Console.WriteLine("String '{0}' contains Low "
+ "Surrogate value at index {1} ",s, i);
else
Console.WriteLine("String '{0}' does't contain any Low"
+ "Surrogate value at index {1}",s, i);
}
}
输出：
String '1234' does't contain any LowSurrogate value at index 3
String 'Tsunami' does't contain any LowSurrogate value at index 3
String 'psyc0lo' does't contain any LowSurrogate value at index 4
String 'að??z' contains Low Surrogate value at index 2
s is null
Exception Thrown: System.ArgumentNullException
示例3：对于ArgumentOutOfRangeException
// C# program to demonstrate
// Char.IsLowSurrogate(String,
// Int32) Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// calling check() Method
check("1234", 3);
check("Tsunami", 3);
check("psyc0lo", 4);
// declaring and initializing string s1
string s1 = new String(new char[] {'a',
'\uD800', '\uDC00', 'z' });
check(s1, 2);
Console.WriteLine("");
Console.WriteLine("index is less than zero");
check("null", -4);
}
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);
}
}
// Defining check() method
public static void check(string s, int i)
{
// checking condition
// using IsLowSurrogate() Method
bool val = Char.IsLowSurrogate(s, i);
// checking
if (val)
Console.WriteLine("String '{0}' contains Low "
+ "Surrogate value at index {1} ",s, i);
else
Console.WriteLine("String '{0}' does't contain any Low"
+ "Surrogate value at index {1}",s, i);
}
}
输出：
String '1234' does't contain any LowSurrogate value at index 3
String 'Tsunami' does't contain any LowSurrogate value at index 3
String 'psyc0lo' does't contain any LowSurrogate value at index 4
String 'að??z' contains Low Surrogate value at index 2
index is less than zero
Exception Thrown: System.ArgumentOutOfRangeException
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.char.islowsurrogate?view=netframework-4.7.2#System_Char_IsLowSurrogate_System_String_System_Int32_