1. 字符串实例方法PadLeft
    PadLeft返回一个指定长度的新字符串，在实例字符串的开头填充空格或指定的 Unicode 字符。通常用于字符串对齐。语法格式：
public string PadLeft(int length);
public string PadLeft(int length, char c);

2. 字符串实例方法PadRight
    PadRight返回一个指定长度的新字符串，在实例字符串的开头填充空格或指定的 Unicode 字符。语法格式：
public string PadRight(int length);
public string PadRight(int length, char c);

3. PadLeft/PadRight方法使用

string padStr01 = "Benz and BMW";
string plStr01 = padStr01.PadLeft(15));         //"   Benz and BMW".
string plStr02 = padStr01.PadLeft(5));          //"Benz and BMW".
string plStr03 = padStr01.PadLeft(15, '.'));    //"...Benz and BMW"
string padStr02 = "C#,Hello World!";
string plStr04 = padStr02.PadRight(20);      //"C#,Hello World!     "
string plStr05 = padStr02.PadRight(13,'!');  //"C#,Hello World!"

4. 字符串实例方法Trim
    Trim方法用于删除指定字符串的前导和结尾空白字符或者指定的字符亦或是字符数组中的字符，并返回一个新的字符串。对应的还有TrimStart()和TrimEnd()实例方法。语法格式：
public string Trim();
public string Trim(char c);
public string Trim(char[] cArray);
public string TrimStart();
public string TrimStart(char c);
public string TrimStart(char[] cArray);
public string TrimEnd();
public string TrimEnd(char c);
public string TrimEnd(char[] cArray);

5. Trim/TrimStart/TrimEnd方法使用

string trimStr01 = "Benz and BMW";
string tstr01 = trimStr01.PadLeft(15)).Trim();         //"Benz and BMW".
string trimStr02 = "C#,Hello World!";
string tstr02 = trimStr02.PadRight(20).TrimEnd();      //"C#,Hello World!     "