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：
<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：
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 )~
var result = Enumerable.Range( 1 , 49 ).OrderBy( d=>Guid.NewGuid() ).Take( 6 );