C#笔记

1.c# String 前面不足位数补零的方法:
String.Format("{0:D5}",16);
or
int i=16;
i.ToString("D5");
Result: 00016

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2.C# Math.Ceiling()向上取整，Math.Floor()向下取整

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3.C#List按两个关键字排序不用orderBy来

 1 //类方法
 2 class StudentComp : IComparer<Student>
 3 {
 4     public int Compare(Student x, Student y)
 5     {
 6         if (x.Age.CompareTo(y.Age) == 0) //年龄相同时按性别降序排列
 7         {
 8             return -(x.Gender.CompareTo(y.Gender));
 9         }
10         else
11         {
12             return -(x.Age.CompareTo(y.Age));//年龄降序排列
13         }
14     }
15 }
16  
17 m_lstStudent.Sort(new StudentComp());
18 ----------------------------------------------------
19 //函数方法
20 public int CompareStudent(Student x, Student y)
21 {
22     if (x.Age.CompareTo(y.Age) == 0) //年龄相同时按性别降序排列
23     {
24         return -(x.Gender.CompareTo(y.Gender));
25     }
26     else
27     {
28         return -(x.Age.CompareTo(y.Age));//年龄降序排列
29     }
30 }
31 
32 m_lstStudent.Sort(CompareStudent);

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4.按长度来给字符串分组

 1 /// <summary>
 2     /// 字符串分割成几组
 3     /// </summary>
 4     /// <param name="strSrc">要分割的字符</param>
 5     /// <param name="step">每多少个字符就分割一组</param>
 6     /// <param name="strSplit">用什麼字符作为分隔符</param>
 7     /// <returns></returns>
 8     public string XSplitString(string strSrc, int step, string strSplit) 
 9     { 
10         int i = 0; 
11         string strDes = "";
12         while (i < strSrc.Length) 
13         {
14             strDes = strDes + strSrc.Substring(i, step) + strSplit; 
15             i += step; 
16         }
17         return strDes; 
18     }