string是我们的朋友。我们离不开string，但是有时候string也挺烦人的。
比如说，下面的代码，根据方法名来获取MethodInfo：
var info
=
typeof
(DateTime).GetMethod(
"
ToShortDateSting
"
);
Console.WriteLine(info.Name);
Console.WriteLine(info.Name);
进行“Rename Method”重构时，重构工具是不会去对string进行重命名的。
我们不得不手动去一个一个改。如果漏了一个，我们也不能能当场知道，等到程序报错时就太晚了！
我们可以通过lambda表达式，来获取MethodInfo：
var info
=
Reflect.GetMethod
<
DateTime
>
(dt
=>
dt.ToShortDateString());
Console.WriteLine(info.Name);
Console.WriteLine(info.Name);
同样，我们可以获取PropertyInfo：
var dayProperty
=
Reflect.GetProperty
<
DateTime
>
(dt
=>
dt.Day);
Console.WriteLine(dayProperty.Name);
Console.WriteLine(dayProperty.Name);
下面是实现代码：
public
static
class
Reflect
{
public static MethodInfo GetMethod < TClass > (Expression < Action < TClass >> expression)
{
var methodCall = expression.Body as MethodCallExpression;
if (methodCall == null )
{
throw new ArgumentException( " Expected method call " );
}
return methodCall.Method;
}
public static PropertyInfo GetProperty < TClass > (Expression < Func < TClass, object >> expression)
{
MemberExpression memberExpression;
var unary = expression.Body as UnaryExpression;
if (unary != null )
{
memberExpression = unary.Operand as MemberExpression;
}
else
{
memberExpression = expression.Body as MemberExpression;
}
if (memberExpression == null || ! (memberExpression.Member is PropertyInfo))
{
throw new ArgumentException( " Expected property expression " );
}
return (PropertyInfo) memberExpression.Member;
}
}
{
public static MethodInfo GetMethod < TClass > (Expression < Action < TClass >> expression)
{
var methodCall = expression.Body as MethodCallExpression;
if (methodCall == null )
{
throw new ArgumentException( " Expected method call " );
}
return methodCall.Method;
}
public static PropertyInfo GetProperty < TClass > (Expression < Func < TClass, object >> expression)
{
MemberExpression memberExpression;
var unary = expression.Body as UnaryExpression;
if (unary != null )
{
memberExpression = unary.Operand as MemberExpression;
}
else
{
memberExpression = expression.Body as MemberExpression;
}
if (memberExpression == null || ! (memberExpression.Member is PropertyInfo))
{
throw new ArgumentException( " Expected property expression " );
}
return (PropertyInfo) memberExpression.Member;
}
}
更实用的例子是，MVC的RedirectToAction方法：
public
class
HomeController : Controller
{
public void Index()
{
if ( ! UserIsLoggedIn)
{
RedirectToAction( " Login " );
}
}
public void Login()
{
}
}
{
public void Index()
{
if ( ! UserIsLoggedIn)
{
RedirectToAction( " Login " );
}
}
public void Login()
{
}
}
用同样的方法，上面的代码，可以重写为：
public
class
HomeController : Controller
{
public void Index()
{
if ( ! UserIsLoggedIn)
{
this .RedirectToAction(c => c.Login());
}
}
}
}
{
public void Index()
{
if ( ! UserIsLoggedIn)
{
this .RedirectToAction(c => c.Login());
}
}
public void Login()
{}
}
下面是实现代码：
public
static
class
ControllerExtensions
{
public static void RedirectToAction < TController > ( this TController controller, Expression < Action < TController >> expression) where TController : Controller
{
var methodCall = expression.Body as MethodCallExpression;
if (methodCall == null )
{
throw new ArgumentException( " Expected method call " );
}
controller.RedirectToAction(methodCall.Method.Name);
}
}
{
public static void RedirectToAction < TController > ( this TController controller, Expression < Action < TController >> expression) where TController : Controller
{
var methodCall = expression.Body as MethodCallExpression;
if (methodCall == null )
{
throw new ArgumentException( " Expected method call " );
}
controller.RedirectToAction(methodCall.Method.Name);
}
}
参考：http://blog.andreloker.de/post/2008/06/Getting-rid-of-strings-%282%29-use-lambda-expressions.aspx
注意：个人意见，仅供参考！
