Simple Thoughts on Everything: 四月 2009

(題目)抓取陣列中最接近且小於輸入值的數

星期三, 四月 29, 2009 | 標籤： C# | 0 意見 |

今天有人問我這個問題"抓取陣列中最接近且小於輸入值的數"..我記錄下來..以後有需要的人可以參考一下..

public static class CompareIntHelper
{
 //過濾比自己小的int[]
 private static int[] GetThenLessArray(int number, int[] randomArr)
 {
     return randomArr.Where(a => a < number).ToArray();
 }
 //抓最接近
 public static int GetThenLessAndClosedNumber(int number, int[] randomArr)
 {
     randomArr = GetThenLessArray(number, randomArr);
     if (randomArr.Length == 0)
         throw new Exception("沒有數字比亂數陣列小");

     int ans = randomArr[0];
     int intTemp = int.MaxValue;
     Array.ForEach(randomArr, a =>
     {
         if (number - a < intTemp)
         {
             ans = a;
             intTemp = number - a;
         }
     });
     return ans;
 }
}

使用如下..

//測試資料
Random r = new Random();
int[] randomArr = new int[1000];
for (int i = 0; i < 1000; i++)
 randomArr[i] = r.Next(0, 10000);
//列出結果
try
{
 Response.Write(CompareIntHelper.GetThenLessAndClosedNumber(1200, randomArr) + "<br />");
}
catch (Exception ex)
{
 Response.Write(ex.Message);
}

--2009/5/1 更新--

經過一些討論..發現只要加入排序..程式就更簡單了..

public static class CompareIntHelper1
{
   //抓最接近,且小於number
   public static int GetThenLessAndClosedNumber(int number, int[] randomArr)
   {
       var result = randomArr.OrderByDescending(a => a).Where(a => number > a);
       if (result.Count() == 0)
           throw new Exception("沒有數字比亂數陣列小");
       return result.First();
   }
}

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Entity Framework 處理關聯資料表

星期四, 四月 23, 2009 | 標籤： ADO.NET | 1 意見 |

有人問我..如果一堆關聯的 table..想用 Entity Framework 去抓取資料..會不會很麻煩..我做個簡單的範例..各位看倌看看ㄅ..

先準備 table..

再來..我希望..以 TableA 的 ID 來作為搜尋條件..找出 TableD 的資料..

using (NORTHWNDModel.NORTHWNDEntities db = new NORTHWNDModel.NORTHWNDEntities())
{
   var aaaa = db.TableD.Where(a => a.TableC.TableB.TableA.ID == 1);
   GridView1.DataSource = aaaa;
   GridView1.DataBind();
}

很簡單ㄅ..如果用 Entity SQL 可以這樣做..

using (NORTHWNDModel.NORTHWNDEntities db = new NORTHWNDModel.NORTHWNDEntities())
{
   var aaaa = db.CreateQuery<NORTHWNDModel.TableD>(
       "select value d from TableD as d where d.TableC.TableB.TableA.ID = 1");
   GridView1.DataSource = aaaa;
   GridView1.DataBind();
}

我們看一下 EntityFramework 幫我們產生出來的 TSQL..

這樣就可以很清楚知道..用 Entity Framework 去處理關聯 Table 是蠻直覺又輕鬆的..在問題在一起討論ㄅ..

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抓出Entity Framework的SQL指令

星期三, 四月 15, 2009 | 標籤： ADO.NET | 0 意見 |

最近在研究Entity Framework..發現EF真的蠻不錯用的..尤其在Linq熟得時候..EF就可以很得心應手..今天在寫的時候..覺得EF丟出的指令還是要試著去了解..因為有時複雜的Linq to Entity還是需要看看怎樣寫才能丟出有效率的SQL Statement..下面就是簡單的兩個方法去抓出SQL Statement..

第一種方法

using (NORTHWNDModel.NORTHWNDEntities db = new NORTHWNDModel.NORTHWNDEntities())
{
   var aaaa = db.Orders.Select(a => new { a.ShipName, a.ShipCity }).Take(10);
   ObjectQuery oq = aaaa as ObjectQuery;
   if (oq != null)
   {
       string SQLStr = oq.ToTraceString();
       Response.Write(SQLStr);
   }
}

第二種方法

using (NORTHWNDModel.NORTHWNDEntities db = new NORTHWNDModel.NORTHWNDEntities())
{
   var aaaa = db.Orders.Select(a => new { a.ShipName, a.ShipCity }).Take(10);
   MethodInfo mi = aaaa.GetType().GetMethod("ToTraceString");
   if (mi != null)
       Response.Write(mi.Invoke(aaaa, null).ToString());
}

結果:

第一種方法效率好很多..如果可以就用第一種方法ㄅ..

參考:

http://msdn.microsoft.com/zh-tw/library/system.data.objects.objectquery.totracestring.aspx

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(題目)如何去抓出雙數周的週六

星期三, 四月 01, 2009 | 標籤： C# | 0 意見 |

今天看到一個題目"如何去抓出雙數周,用來判斷隔週休"..隨手寫了程式..紀錄一下....

這樣執行就可以列出第雙數週週六了

WeekSpProvider wp = new WeekSpProvider(2009, 4, DayOfWeek.Saturday, 12);
var data = wp.GetDateTimeList(2);
foreach (var a in data)
   Response.Write(a.Date.ToString("yyyy/MM/dd")+"<br />");

class:

/// <summary>
/// 來處理數個月的資料
/// </summary>
public class WeekSpProvider
{
   List<DateObj> dateTimeList = new List<DateObj>();
   public WeekSpProvider(int startYear, int startMonth, DayOfWeek dayWeek, int monthCount)
   {
       DateTime dtStart = new DateTime(startYear, startMonth, 1);
       for (int i = 1; i <= monthCount; i++)
       {
           MonthObj mo = new MonthObj(dtStart, dayWeek);
           this.dateTimeList = this.dateTimeList
               .Union(mo.GetDateTimeList()).ToList();
           dtStart = dtStart.AddMonths(1);
       }
   }
   /// <summary>
   /// 找到倍數的週數
   /// </summary>
   /// <param name="multiplier"></param>
   /// <returns></returns>
   public List<DateObj> GetDateTimeList(int multiplier)
   {
       return this.dateTimeList.Where(a => a.Number % multiplier == 0).ToList();
   }
}
/// <summary>
/// 處理一個月的月份
/// </summary>
public class MonthObj
{
   int year;
   int month;
   List<DateObj> dateTimeList = new List<DateObj>();
   DateTime nextMonth;
   DayOfWeek dayWeek;
   public MonthObj(DateTime dt, DayOfWeek dayWeek)
   {
       this.year = dt.Year;
       this.month = dt.Month;
       this.dayWeek = dayWeek;
       //抓出這個月第一天,跟下個月的第一天
       DateTime dateTime = new DateTime(year, month, 1);
       nextMonth = dateTime.AddMonths(1);
       //迴圈去取得每一周
       int i = 0;
       do
       {
           if (IsYouWantDay(dateTime))
           {
               AddDate(++i, dateTime);
               dateTime = dateTime.AddDays(7);
           }
           else
           {
               dateTime = dateTime.AddDays(1);
           }
       }
       while (dateTime < nextMonth);
   }
   public List<DateObj> GetDateTimeList()
   {
       return dateTimeList;
   }
   private void AddDate(int number, DateTime dt)
   {
       if (dt < nextMonth)
           this.dateTimeList.Add(
               new DateObj() { Number = number, Month = dt.Month, Date = dt, DayWeek = dayWeek });
   }
   private bool IsYouWantDay(DateTime dt)
   {
       return dt.DayOfWeek == dayWeek;
   }
}
/// <summary>
/// 來紀錄日期的資料
/// </summary>
public struct DateObj
{
   public int Number { get; set; }
   public int Month { get; set; }
   public DayOfWeek DayWeek { get; set; }
   public DateTime Date { get; set; }
}