C#String.PadLeft函数，文本对齐以及填补解决方案。
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由于很多时候我们需要把数据进行格式化，方便各个系统之间通信和数据交互，因此难免会经常让人位数不够而进行位数相应数据填充。比如，你希望获取的是7位的2进制数据格式，而2进制数据格式，都是以0，1都为数据信号的，只有1,0两数据格式，刚我说的是7位，相当于如下：1000101格式，如果，我的数据是101三个长度的2进制数据，但我想返回一个新的并且具有固定长度，位数不够填充0的做法。
string SourceStr="101";
string DestinationStr;
DestinationStr=String.PadLeft(7,"0");
Console.Write(DestinationStr);
以上代码就会输出：0000101
现在解析此函数，此函数有2个重载版本。
重载1：public string PadLeft(int totalWidth);
重载2public string PadLeft(int totalWidth, char paddingChar);
关于重载1的解释，微软的注释为：(这个默认是以空格进行左边填充，保持右边对齐。)
//
// Summary:
// Right-aligns the characters in this instance, padding with spaces on the
// left for a specified total length.
//
// Parameters:
// totalWidth:
// The number of characters in the resulting string, equal to the number of
// original characters plus any additional padding characters.
//
// Returns:
// A new System.String that is equivalent to this instance, but right-aligned
// and padded on the left with as many spaces as needed to create a length of
// totalWidth. Or, if totalWidth is less than the length of this instance, a
// new System.String object that is identical to this instance.
//
// Exceptions:
// System.ArgumentOutOfRangeException:
// totalWidth is less than zero.
public string PadLeft(int totalWidth);
// Summary:
// Right-aligns the characters in this instance, padding with spaces on the
// left for a specified total length.
//
// Parameters:
// totalWidth:
// The number of characters in the resulting string, equal to the number of
// original characters plus any additional padding characters.
//
// Returns:
// A new System.String that is equivalent to this instance, but right-aligned
// and padded on the left with as many spaces as needed to create a length of
// totalWidth. Or, if totalWidth is less than the length of this instance, a
// new System.String object that is identical to this instance.
//
// Exceptions:
// System.ArgumentOutOfRangeException:
// totalWidth is less than zero.
public string PadLeft(int totalWidth);
而重载2的注释为：（可以根据自己想要填充的字符进行填充，对齐是字符串右对齐。）
代码
//
// Summary:
// Right-aligns the characters in this instance, padding on the left with a
// specified Unicode character for a specified total length.
//
// Parameters:
// totalWidth:
// The number of characters in the resulting string, equal to the number of
// original characters plus any additional padding characters.
//
// paddingChar:
// A Unicode padding character.
//
// Returns:
// A new System.String that is equivalent to this instance, but right-aligned
// and padded on the left with as many paddingChar characters as needed to create
// a length of totalWidth. Or, if totalWidth is less than the length of this
// instance, a new System.String that is identical to this instance.
//
// Exceptions:
// System.ArgumentOutOfRangeException:
// totalWidth is less than zero.
public string PadLeft(int totalWidth, char paddingChar);
// Summary:
// Right-aligns the characters in this instance, padding on the left with a
// specified Unicode character for a specified total length.
//
// Parameters:
// totalWidth:
// The number of characters in the resulting string, equal to the number of
// original characters plus any additional padding characters.
//
// paddingChar:
// A Unicode padding character.
//
// Returns:
// A new System.String that is equivalent to this instance, but right-aligned
// and padded on the left with as many paddingChar characters as needed to create
// a length of totalWidth. Or, if totalWidth is less than the length of this
// instance, a new System.String that is identical to this instance.
//
// Exceptions:
// System.ArgumentOutOfRangeException:
// totalWidth is less than zero.
public string PadLeft(int totalWidth, char paddingChar);
同理关于PadRight的用法和这个也是完全相似，只是这个是在后面补充，或者填充自己想要的字符。
