C#实现数字字符串左补零的六种方式技巧

string number = "42";  
string paddedNumber = number.PadLeft(5, '0'); // 结果是 "00042"  

int number = 42; string paddedNumber = String.Format("{0:D5}", number); // 结果是 "00042" 

int number = 42;  
string paddedNumber = $"{number:D5}"; // 结果是 "00042"  

int number = 42;  
string paddedNumber = number.ToString("D5"); // 结果是 "00042"  

string number = "123";  
int totalLength = 8;  
char paddingChar = '0';  

StringBuilder sb = new StringBuilder();  
int paddingLength = totalLength - number.Length;  

for (int i = 0; i < paddingLength; i++)  
{  
    sb.Append(paddingChar);  
}  

sb.Append(number);  

string paddedNumber = sb.ToString();  

Console.WriteLine(paddedNumber); // 输出: 00000123  

string[] numbers = { "1", "23", "456" };  
string[] paddedNumbers = numbers.Select(n => n.PadLeft(5, '0')).ToArray();   

// 输出: ["00001", "00023", "00456"]