以前一直用 var query = xxx.Select(c=>new {c.X,c.Y}); 来取表中的某二列字段，今天有个应用需要转成Dictionary<T,U>，很少这样使用，居然忘记了写法！
回忆了半天终于写对了，贴在这里备个份，方便以后查找:
using
System;
using System.Collections.Generic;
using System.Linq;
namespace DicTest
{
class Program
{
static void Main( string [] args)
{
List < Test > lst = new List < Test > ();
for ( int i = 0 ; i < 10 ; i ++ )
{
lst.Add( new Test() { Id = Guid.NewGuid(), Num = i, Name = i.ToString() });
}
Dictionary < Guid, int > dic = lst.ToDictionary( new Func < Test, Guid > (c => c.Id), new Func < Test, int > (c => c.Num));
using System.Collections.Generic;
using System.Linq;
namespace DicTest
{
class Program
{
static void Main( string [] args)
{
List < Test > lst = new List < Test > ();
for ( int i = 0 ; i < 10 ; i ++ )
{
lst.Add( new Test() { Id = Guid.NewGuid(), Num = i, Name = i.ToString() });
}
Dictionary < Guid, int > dic = lst.ToDictionary( new Func < Test, Guid > (c => c.Id), new Func < Test, int > (c => c.Num));
//如果觉得上面的写法太复杂，还可以简化为
// Dictionary<Guid, int> dic = lst.ToDictionary(c => c.Id, c => c.Num);
foreach (Guid Id in dic.Keys)
{
Console.WriteLine( " Key:{0}\tValue:{1} " , Id, dic[Id]);
}
Console.Read();
}
}
public class Test
{
public Guid Id { set ; get ; }
public int Num { set ; get ; }
public string Name { set ; get ; }
}
}
foreach (Guid Id in dic.Keys)
{
Console.WriteLine( " Key:{0}\tValue:{1} " , Id, dic[Id]);
}
Console.Read();
}
}
public class Test
{
public Guid Id { set ; get ; }
public int Num { set ; get ; }
public string Name { set ; get ; }
}
}
如果用Reflector反射一下，会发现实际上编译器自动生成了类似以下代码:(部分名称做了友好处理)
代码
[CompilerGenerated]
private static Func < Test, Guid > funcGuid;
[CompilerGenerated]
private static Func < Test, int > funcInt;
[CompilerGenerated]
private static int mNum(Test c)
{
return c.Num;
}
[CompilerGenerated]
private static Guid mId(Test c)
{
return c.Id;
}
private static void Main( string [] args)
{
List < Test > lst = new List < Test > ();
for ( int i = 0 ; i < 10 ; i ++ )
{
Test _t = new Test();
_t.Id = Guid.NewGuid();
_t.Num = i;
_t.Name = i.ToString();
lst.Add(_t);
}
Dictionary < Guid, int > dic = lst.ToDictionary < Test, Guid, int > ((funcGuid != null ) ? funcGuid : (funcGuid = new Func < Test, Guid > (Program.mId)), (funcInt != null ) ? funcInt : (funcInt = new Func < Test, int > (Program.mNum)));
foreach (Guid Id in dic.Keys)
{
Console.WriteLine( " Key:{0}\tValue:{1} " , Id, dic[Id]);
}
Console.Read();
}
private static Func < Test, Guid > funcGuid;
[CompilerGenerated]
private static Func < Test, int > funcInt;
[CompilerGenerated]
private static int mNum(Test c)
{
return c.Num;
}
[CompilerGenerated]
private static Guid mId(Test c)
{
return c.Id;
}
private static void Main( string [] args)
{
List < Test > lst = new List < Test > ();
for ( int i = 0 ; i < 10 ; i ++ )
{
Test _t = new Test();
_t.Id = Guid.NewGuid();
_t.Num = i;
_t.Name = i.ToString();
lst.Add(_t);
}
Dictionary < Guid, int > dic = lst.ToDictionary < Test, Guid, int > ((funcGuid != null ) ? funcGuid : (funcGuid = new Func < Test, Guid > (Program.mId)), (funcInt != null ) ? funcInt : (funcInt = new Func < Test, int > (Program.mNum)));
foreach (Guid Id in dic.Keys)
{
Console.WriteLine( " Key:{0}\tValue:{1} " , Id, dic[Id]);
}
Console.Read();
}
PS:今天写的好象都是些水文 :)
