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

//类方法
class StudentComp : IComparer<Student>
{
    public int Compare(Student x, Student y)
    {
        if (x.Age.CompareTo(y.Age) == 0) //年龄相同时按性别降序排列
        {
            return -(x.Gender.CompareTo(y.Gender));
        }
        else
        {
            return -(x.Age.CompareTo(y.Age));//年龄降序排列
        }
    }
}
 
m_lstStudent.Sort(new StudentComp());
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//函数方法
public int CompareStudent(Student x, Student y)
{
    if (x.Age.CompareTo(y.Age) == 0) //年龄相同时按性别降序排列
    {
        return -(x.Gender.CompareTo(y.Gender));
    }
    else
    {
        return -(x.Age.CompareTo(y.Age));//年龄降序排列
    }
}

m_lstStudent.Sort(CompareStudent);

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4.按长度来给字符串分组

/// <summary>
    /// 字符串分割成几组
    /// </summary>
    /// <param name="strSrc">要分割的字符</param>
    /// <param name="step">每多少个字符就分割一组</param>
    /// <param name="strSplit">用什麼字符作为分隔符</param>
    /// <returns></returns>
    public string XSplitString(string strSrc, int step, string strSplit) 
    { 
        int i = 0; 
        string strDes = "";
        while (i < strSrc.Length) 
        {
            strDes = strDes + strSrc.Substring(i, step) + strSplit; 
            i += step; 
        }
        return strDes; 
    }