转帖 [C#][Silverlight]透過LINQ取得不重複的隨機數值

日前在專案中有需要從題庫中隨機挑選題目的需求，加上最近在MSDN論壇看到有人在問隨機取得不重複的數值的問題，為了避免之後又不小心忘記這個方便的寫法，特別寫文章來紀錄一下。

首先，請直接看這個範例(請別把這個範例當作明牌產生器喔!!槓龜我可不負責~)：

接著看看原始碼：

MainPage.xaml

<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  xmlns:theme="clr-namespace:System.Windows.Controls.Theming;assembly=System.Windows.Controls.Theming.ExpressionDark"
  xmlns:toolkit="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit"
  x:Class="SL_RandomWithLinq.MainPage" mc:Ignorable="d" d:DesignHeight="600" d:DesignWidth="800">
 <theme:ExpressionDarkTheme Background="{x:Null}" Foreground="#FF646464">
  <Border BorderThickness="2" CornerRadius="10" Margin="10" Background="White" BorderBrush="#FF646464">
   <Border.Effect>
    <DropShadowEffect />
   </Border.Effect>
   <Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
     <RowDefinition Height="40" />
     <RowDefinition />
     <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <TextBlock HorizontalAlignment="Center" TextWrapping="Wrap" Text="Silverlight 透過Linq取亂數範例"
      VerticalAlignment="Center" FontSize="26.667" FontWeight="Bold" />
    <Rectangle Fill="#FF646464" Height="2" Margin="10,0" VerticalAlignment="Bottom" />
    <TextBlock HorizontalAlignment="Center" TextWrapping="Wrap" Text="第 00000 期大樂透得獎號碼"
      VerticalAlignment="Top" FontSize="32" FontWeight="Bold" Grid.Row="1" Margin="10,10,0,0"
      FontStyle="Italic" Foreground="#FFFFC700">
     <TextBlock.Effect>
      <DropShadowEffect ShadowDepth="1" />
     </TextBlock.Effect></TextBlock>
    <toolkit:WrapPanel x:Name="wrpNumbers" Margin="10,60,10,10" Grid.Row="1">
     <toolkit:WrapPanel.Effect>
      <DropShadowEffect Opacity="0.5" ShadowDepth="1" />
     </toolkit:WrapPanel.Effect>
    </toolkit:WrapPanel>
    <Button x:Name="btnRandom" Content="重新開獎" HorizontalAlignment="Center" Grid.Row="3"
      VerticalAlignment="Center" Margin="0,5,0,10" Padding="10,5" FontSize="16"
      Click="btnRandom_Click" />
   </Grid>
  </Border>
 </theme:ExpressionDarkTheme>
</UserControl>

CodeBehind：

MainPage.xaml.cs

using System;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
namespace SL_RandomWithLinq
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
            for( int i = 1 ; i <= 49 ; i++ )
            {
                this.wrpNumbers.Children.Add( new TextBlock
                                                {
                                                    Text = i.ToString( "00" ) ,
                                                    Foreground = new SolidColorBrush { Color = Colors.Gray } ,
                                                    FontSize = 32 ,
                                                    Width = 80 ,
                                                    Margin = new Thickness( 5 ) ,
                                                    TextAlignment = TextAlignment.Center ,
                                                } );
            }
        }
        private void btnRandom_Click( object sender , RoutedEventArgs e )
        {
            //重置所有號碼為灰色
            this.wrpNumbers.Children.OfType<TextBlock>().ToList().ForEach( t => t.Foreground = new SolidColorBrush { Color = Colors.Gray } );
            //將數值打亂之後透過Take方法取出前6個值
            var result = Enumerable.Range( 1 , 49 ).OrderBy( n => n * n * ( new Random() ).Next() ).Take( 6 );
            //將被挑選出來的號碼改為紅色
            result.ToList().ForEach( i => this.wrpNumbers.Children.OfType<TextBlock>().ElementAt( i - 1 ).Foreground = new SolidColorBrush { Color = Colors.Red } );
        }

    }
}

透過LINQ，真的很威能啊!!原本可能得要透過迴圈才能完成的動作，改由LINQ來實作，就真的只需要一行!!沒錯!!一行!!

不過，您可能會擔心取出來的亂數不夠亂--別擔心，這個寫法是有參考洋人墨水的(參考連結在此：Generating random sequences with LINQ )~

Posted by demo on 2011/10/15 下午 10:32 回覆

我比較習慣直接用 Guid 去排
var result = Enumerable.Range( 1 , 49 ).OrderBy( d=>Guid.NewGuid() ).Take( 6 );