文章閱讀順序建議:
本系列有一個遞進的順序,可依次閱讀以下的文章:
一、採用Delegate對一個未知類型的對象進行"遍歷"
二、採用表達式樹(Expression Tree)對一個對象的屬性進行“遍歷”
三、 採用表達式樹(Expression Block)對一個對象的屬性進行“遍歷”
由於有時候需要對一個不知類型的object進行“遍歷”,得到它的所有公有的屬性和字段。雖然可以採用反射來實現,但是代價太高了,特別是要多次執行時。因此,我寫了一個用Delegate來實現的方法,供大家參考和交流。
我定義了MemberAccessor.dll。裏面有四個文件,具體的內容如下:
定義一個獲得對象的某個Member的Value的接口:IMemberAccessor.cs
namespace MemberAccessor
{
/// <summary>
/// 獲得Member值的接口
/// </summary>
public interface IMemberAccessor
{
object GetValue(object instance);
}
}
定義一個獲取指定類型的指定屬性的GetValue的類: PropertyDelegateAccessor.cs
using System;
using System.Reflection;
namespace MemberAccessor
{
/// <summary>
/// 針對PropertyInfo,生成一個能夠獲得PropertyInfo Value的實例
/// </summary>
/// <typeparam name="TType"></typeparam>
/// <typeparam name="TMember"></typeparam>
public class PropertyDelegateAccesstor<TType, TMember> : IMemberAccessor
{
private Func<TType, TMember> m_getValueDelegate;
public PropertyDelegateAccesstor(Type type, MethodInfo methodInfo)
{
m_getValueDelegate =
(Func<TType, TMember>) Delegate.CreateDelegate(typeof (Func<TType, TMember>), null, methodInfo);
}
public object GetValue(object instance)
{
return m_getValueDelegate((TType)instance);
}
}
}
定義一個獲取指定類型的指定字段的GetValue的類:FieldDelegateAccessor
using System;
using System.Reflection;
namespace MemberAccessor
{
/// <summary>
/// 提交一個FieldInfo,生成一個獲得該FieldInfo Value的實例
/// </summary>
public class FieldDelegateAccessor:IMemberAccessor
{
private Func<object, object> m_getValueDelegate;
public FieldDelegateAccessor(FieldInfo fieldInfo)
{
m_getValueDelegate = fieldInfo.GetValue;
}
public object GetValue(object instance)
{
return m_getValueDelegate(instance);
}
}
}
利用上面的三個接口與類,生成一個針對指定類型的所有屬性與字段訪問的類:InstanceDelegateAccessor.cs
using System;
using System.Collections.Generic;
using System.Reflection;
namespace MemberAccessor
{
/// <summary>
/// 針對某一個類型的實例,生成一個獲得該類型的相應Property與Field 值的實例
/// </summary>
public class InstanceDelegateAccessor
{
private Dictionary<string, IMemberAccessor> m_memberAccessors;
public InstanceDelegateAccessor(Type type, BindingFlags propertyBindingFlags, BindingFlags fieldBindingFlags)
{
m_memberAccessors = new Dictionary<string, IMemberAccessor>();
#region create accessor
//property
var pis = type.GetProperties(propertyBindingFlags);
foreach (var pi in pis)
{
var name = pi.Name;
var accessor =
Activator.CreateInstance(
typeof (PropertyDelegateAccesstor<,>).MakeGenericType(type, pi.PropertyType), type, pi.GetGetMethod()) as
IMemberAccessor;
m_memberAccessors.Add(name, accessor);
}
//field
var fis = type.GetFields(fieldBindingFlags);
foreach (var fi in fis)
{
var name = fi.Name;
var accessor = new FieldDelegateAccessor(fi);
m_memberAccessors.Add(name, accessor);
}
#endregion
}
public object GetValue(object instance, string memberName)
{
if (instance == null || string.IsNullOrWhiteSpace(memberName))
{
throw new ArgumentNullException("input paremeters have null value.");
}
IMemberAccessor accessor = null;
if (m_memberAccessors.TryGetValue(memberName, out accessor) == false || accessor == null)
{
throw new ArgumentException("can not find any MemberDelegate for memberName:" + memberName);
}
return accessor.GetValue(instance);
}
}
/// <summary>
/// 返回一個類的所有字段,屬性的序列對:
/// Prop: Value
/// Field: Value
/// </summary>
/// <param name="instance"></param>
/// <returns></returns>
public IList<Tuple<object,object>> GetValues(object instance)
{
var objs = new List<Tuple<object, object>>();
foreach (var key in m_memberAccessors.Keys)
{
var value = GetValue(instance, key);
objs.Add(new Tuple<object, object>(key, value));
}
return objs;
}
}
最後,測試:
說明:
在Main方法裏先創建兩個對象,一個是StringTest,另一個是IntTest。並創建與它們類型相對應的InstanceDelegateAccessor對象。
最後分別調用ShowAllPublicValue,將對象和它對應的InstanceDelegateAccessor對象作爲參數傳入,再在該方法裏打印對應的屬性與字段。
using System;
using System.Reflection;
using MemberAccessor;
namespace Study
{
public class Test
{
public string stringField;
public int IntProperty { get; set; }
public Test(int prop )
{
stringField = "stringField value";
IntProperty = prop;
}
}
public class Program
{
public static void Main(string[] args)
{
InstanceDelegateAccessor ida = null;
int total = 10; //多個相同的類,採用同一個Serializer即可
for (int i = 0; i < total; ++i)
{
//新建的Object
Test test = new Test(i);
if (ida == null)
{
//沒有Serializer,新建
ida = new InstanceDelegateAccessor(test.GetType(), BindingFlags.Public | BindingFlags.Instance,
BindingFlags.Instance | BindingFlags.Public);
}
//返回的結果:
var results = ida.GetValues(test);
foreach (var result in results)
{
Console.WriteLine(result.Item1 + ": " + result.Item2);
}
Console.WriteLine();
}
}
}
}
有一點不足的是,如果一個類裏引用了另一個類的對象,這樣的話,就只能調用默認的ToString函數了,而不是這個對象的屬性了。
比如說:
class A{
public B b;
}
class B{
public int Bid{get;set;}
}
則一旦我去獲取A的所有字段,那麼對於A裏的b對象,我就只能得到b的ToString()方法返回的結果,我無法得到B裏的屬性Bid。
有知道如何獲得的朋友,希望交流。
參考:http://www.cnblogs.com/nankezhishi/archive/2012/02/11/dynamicaccess.html#di