DynamicMethodFactory。前者提供了一種經過封裝的，簡化Emit方法（包括Emit DynamicMethod，Constructor，Method，get、set Method of Property）的方案；后者基于前者，實現了一種訪問指定類（可以是第三方程序集的internal類）的方法或成員變量，實例化第三方程序集中的internal類型，高性能的以非泛型語法訪問泛型方法的機制（通過DynamicMethod和Delegate實現）。

下載源碼： NBear.Common.zip

介紹

CodeGenerator

該類很多地方參照了.NET 3.0的System.Runtime.Serialization.dll中的同名internal類，他封裝了Emit中的各種Emit層面的常用操作邏輯，包括Ld各種value、成員變量，if-else，case switch，loop等分支控制等，擴展的版本使用DesignByContract對所有的輸入參數進行了檢查，并擴展了對Emit Constructor，Method，get、set Method of Property的支持。

關于Emit DynamicMethod的示例，大家可以參見稍后介紹的 DynamicMethodFactory 類，這里先給出一個使用該類Emit一個類，并實現一個接口的示例代碼，該示例代碼為包含于源碼的 CodeGenerator .cs文件末尾的UnitTest代碼：

?1 ???? namespace ?CodeGeneratorUnitTest
?2 ???? {
?3 ???????? public ? interface ?ITest
?4 ???????? {
?5 ???????????? string ?Wow( string ?str);
?6 ????????}
?7
?8 ???????? public ? class ?UnitTest
?9 ???????? {
10 ???????????? public ? static ? void ?TestEmitInterface()
11 ???????????? {
12 ????????????????AssemblyName?assName? = ? new ?AssemblyName( " TestEmitInterface " );
13 ????????????????AssemblyBuilder?assBuilder? = ?AppDomain.CurrentDomain.DefineDynamicAssembly(assName,?AssemblyBuilderAccess.Run);
14 ????????????????ModuleBuilder?modBuilder? = ?assBuilder.DefineDynamicModule(assBuilder.GetName().Name);
15 ????????????????TypeBuilder?typeBuilder? = ?modBuilder.DefineType( " TestEmitInterface.TestImpl " ,?TypeAttributes.Public);
16 ????????????????typeBuilder.AddInterfaceImplementation( typeof (ITest));
17
18 ????????????????CodeGenerator?ctor? = ? new ?CodeGenerator(typeBuilder,? " ctor " ,?MethodAttributes.Public,?CallingConventions.Standard,? null ,?Type.EmptyTypes);
19 ????????????????ctor.Ldarg( 0 );
20 ????????????????ctor.Call( typeof ( object ).GetConstructor(Type.EmptyTypes));
21 ????????????????ctor.Ret();
22
23 ????????????????MethodInfo?mi? = ? typeof (ITest).GetMethod( " Wow " );
24
25 ????????????????CodeGenerator?wow? = ? new ?CodeGenerator(typeBuilder,?mi.Name,?mi.Attributes? & ?( ~ MethodAttributes.Abstract)? | ?MethodAttributes.Public,?mi.CallingConvention,?mi.ReturnType,? new ?Type[]? {? typeof ( string )?} );
26 ????????????????wow.Ldarg( 1 );
27 ????????????????wow.Ret();
28
29 ????????????????typeBuilder.DefineMethodOverride(wow.CurrentMethod,?mi);
30
31 ????????????????Type?testImplType? = ?typeBuilder.CreateType();
32 ????????????????ITest?test? = ?(ITest)Activator.CreateInstance(testImplType);
33 ????????????????Check.Assert(test.Wow( " hello " )? == ? " hello " );
34 ????????????}
35 ????????}
36 ????}

以上代碼Emit了一個TestImpl類，它實現了ITest接口，包含一個默認構造函數和一個Wow方法，注意，構造函數和方法都是通過CodeGenerator Emit的，這里的邏輯比較簡單，但應該已經能看到相對于ilGen.Emit(OpCodes.XXX, YYY)這樣的語法的簡化，如果實現邏輯復雜，對整個Emit過程的簡化就更明顯。

DynamicMethodFactory

該類的主要功能包括：實例化第三方程序集中的internal類型（ DynamicMethodFactory. CreateInstance()方法），為指定類型（可以是第三方程序集中的internal類型）的泛型或非泛型方法、屬性、字段的讀寫生成非強類型的Delegate（通過DynamicMethod實現，不使用反射，性能接近直接訪問）。

下面先給出一個該類中為一個Method創建一個DynamicMethod，并返回其Delegate的示例，DynamicMethod是使用前面介紹的CodeGenerator實現的：

?1 ???????? protected ? static ?DynamicMethodProxyHandler?DoGetMethodDelegate(
?2 ????????????Module?targetModule,
?3 ????????????MethodInfo?genericMethodInfo,
?4 ???????????? params ?Type[]?genericParameterTypes)
?5 ???????? {
?6 ???????????? Check?preconditions #region ?Check?preconditions
?7
?8 ????????????Check.Require(targetModule,? " targetModule " );
?9 ????????????Check.Require(genericMethodInfo,? " genericMethodInfo " );
10 ????????????Check.Require((genericParameterTypes? == ? null ? && ?genericMethodInfo.GetGenericArguments().Length? == ? 0 )? ||
11 ????????????????genericParameterTypes.Length? == ?genericMethodInfo.GetGenericArguments().Length,
12 ???????????????? " The?number?of?generic?type?parameter?of?genericMethodInfo?and?the?input?types?must?equal! " );
13 ????????????Check.Require( ! genericMethodInfo.IsStatic,? " genericMethodInfo?must?not?be?static?here! " );
14
15 ???????????? #endregion
16
17 ???????????? // Create?a?dynamic?method?proxy?delegate?used?to?call?the?specified?methodinfo
18 ????????????CodeGenerator?gen? = ? new ?CodeGenerator(targetModule);
19 ????????????gen.BeginMethod( " dm " ? + ?Guid.NewGuid().ToString( " N " ),? typeof (DynamicMethodProxyHandler));
20 ????????????MethodInfo?makeGenericMethodInfo? = ?MakeMethodGeneric(genericMethodInfo,?genericParameterTypes);
21 ????????????gen.Ldarg( 0 );
22 ????????????LoadParameters(gen,?makeGenericMethodInfo.GetParameters(),? false );
23 ????????????gen.Call(makeGenericMethodInfo);
24 ????????????CastValueToObject(gen,?makeGenericMethodInfo.ReturnType);
25
26 ???????????? return ?(DynamicMethodProxyHandler)gen.EndMethod();
27 ????????}

LoadParameters和CastValueToObject的代碼
?1 ???????? private ? static ? void ?LoadParameters(CodeGenerator?gen,?ParameterInfo[]?pis,? bool ?isMethodStatic)
?2 ???????? {
?3 ????????????Check.Require(gen,? " gen " );
?4
?5 ???????????? if ?(pis? != ? null )
?6 ???????????? {
?7 ???????????????? for ?( int ?i? = ? 0 ;?i? < ?pis.Length;? ++ i)
?8 ???????????????? {
?9 ???????????????????? if ?(isMethodStatic)
10 ???????????????????? {
11 ????????????????????????gen.Ldarg( 0 );
12 ????????????????????}
13 ???????????????????? else
14 ???????????????????? {
15 ????????????????????????gen.Ldarg( 1 );
16 ????????????????????}
17 ????????????????????gen.Ldc(i);
18
19 ????????????????????Type?srcType? = ?pis[i].ParameterType;
20 ???????????????????? string ?str? = ?srcType.ToString();
21 ???????????????????? if ?(str.EndsWith( " & " ))
22 ???????????????????? {
23 ????????????????????????srcType? = ?CommonUtils.GetType(str.Substring( 0 ,?str.Length? - ? 1 ));
24 ????????????????????}
25
26 ???????????????????? if ?(str.EndsWith( " & " ))? // ref?or?out?param
27 ???????????????????? {
28 ???????????????????????? if ?(srcType.IsValueType? && ?(pis[i].Attributes? & ?ParameterAttributes.Out)? != ?ParameterAttributes.Out)? // ref?value?param
29 ???????????????????????? {
30 ????????????????????????????gen.Ldelem( typeof ( object ));
31 ????????????????????????????gen.Unbox(srcType);
32 ????????????????????????}
33 ???????????????????????? else
34 ???????????????????????? {
35 ???????????????????????????? if ?(srcType.IsValueType? && ?srcType? != ? typeof ( object ))? // out?value?param
36 ???????????????????????????? {
37 ????????????????????????????????gen.LoadDefaultValue(srcType);
38 ????????????????????????????????gen.Box(srcType);
39 ????????????????????????????????gen.Stelem( typeof ( object ));
40
41 ???????????????????????????????? if ?(isMethodStatic)
42 ???????????????????????????????? {
43 ????????????????????????????????????gen.Ldarg( 0 );
44 ????????????????????????????????}
45 ???????????????????????????????? else
46 ???????????????????????????????? {
47 ????????????????????????????????????gen.Ldarg( 1 );
48 ????????????????????????????????}
49 ????????????????????????????????gen.Ldc(i);
50 ????????????????????????????????gen.Ldelem( typeof ( object ));
51 ????????????????????????????????gen.Unbox(srcType);
52 ????????????????????????????}
53 ???????????????????????????? else ? // ref?or?out?class?param
54 ???????????????????????????? {
55 ????????????????????????????????gen.Ldelema( typeof ( object ));
56 ????????????????????????????}
57 ????????????????????????}
58 ????????????????????}
59 ???????????????????? else
60 ???????????????????? {
61 ????????????????????????gen.Ldelem( typeof ( object ));
62
63 ???????????????????????? if ?(srcType.IsValueType)
64 ???????????????????????? {
65 ????????????????????????????gen.UnboxAny(srcType);
66 ????????????????????????}
67 ???????????????????????? else ? if ?(srcType? != ? typeof ( object ))
68 ???????????????????????? {
69 ????????????????????????????gen.Castclass(srcType);
70 ????????????????????????}
71 ????????????????????}
72 ????????????????}
73 ????????????}
74 ????????}
75
76 ???????? private ? static ? void ?CastValueToObject(CodeGenerator?gen,?Type?valueType)
77 ???????? {
78 ???????????? if ?(valueType? == ? typeof ( void ))
79 ???????????? {
80 ????????????????gen.Load( null );
81 ????????????}
82 ???????????? else ? if ?(valueType.IsValueType)
83 ???????????? {
84 ????????????????gen.Box(valueType);
85 ????????????}
86 ???????????? else ? if ?(valueType? != ? typeof ( object ))
87 ???????????? {
88 ????????????????gen.Castclass( typeof ( object ));
89 ????????????}
90 ????????}

代碼是不是相對比較簡單呢（當然是相對于自己寫所有的Emit來講的），注意這里的LoadParameter方法的實現您可以發現，為方法生成調用Delegate是完美支持輸入輸出參數的。

下面給出

DynamicMethodFactory類的UnitTest代碼，演示了對方法、字段和屬性的生成Delegate和基于Delegate的讀寫，且包括對輸入輸出參數的使用：

??1 ???? namespace ?DynamicMethodFactoryUnitTest
??2 ???? {
??3 ???????? public ? class ?TestClass
??4 ???????? {
??5 ???????????? public ? static ? void ?StaticReturnVoidMethod()
??6 ???????????? {
??7 ????????????}
??8
??9 ???????????? public ? static ? int ?StaticReturnIntMethod( string ?str,? int ?i,? ref ? int ?refInt,? ref ? string ?refStr)
?10 ???????????? {
?11 ????????????????Check.Assert(str? == ? " str " );
?12 ????????????????Check.Assert(i? == ? 1 );
?13 ????????????????Check.Assert(refInt? == ? 3 );
?14 ????????????????Check.Assert(refStr? == ? " instr " );
?15
?16 ???????????????? int ?ret? = ?i? + ?refInt;
?17 ????????????????refInt? = ?i? + ? 1 ;
?18 ????????????????refStr? = ? " ref " ? + ?str;
?19
?20 ????????????????Check.Assert(refInt? == ? 2 );
?21 ????????????????Check.Assert(ret? == ? 4 );
?22 ????????????????Check.Assert(refStr? == ? " refstr " );
?23
?24 ???????????????? return ?ret;
?25 ????????????}
?26
?27 ???????????? public ? static ? int ?StaticIntField;
?28
?29 ???????????? public ? static ? int ?StaticIntProperty
?30 ???????????? {
?31 ???????????????? get
?32 ???????????????? {
?33 ???????????????????? return ?StaticIntField;
?34 ????????????????}
?35 ???????????????? set
?36 ???????????????? {
?37 ????????????????????StaticIntField? = ?value;
?38 ????????????????}
?39 ????????????}
?40
?41 ???????????? public ? void ?NonStaticReturnVoidMethod()
?42 ???????????? {
?43 ????????????}
?44
?45 ???????????? public ? int ?NonStaticReturnIntMethod( string ?str,? int ?i,? out ? int ?outInt,? out ? string ?outStr)
?46 ???????????? {
?47 ????????????????outInt? = ?i? + ? 1 ;
?48 ????????????????Check.Assert(outInt? == ? 2 );
?49 ????????????????outStr? = ? " out " ? + ?str;
?50 ????????????????Check.Assert(outStr? == ? " outstr " );
?51 ???????????????? return ?i? + ? 2 ;
?52 ????????????}
?53
?54 ???????????? public ? int ?NonStaticIntField;
?55
?56 ???????????? public ? int ?NonStaticIntProperty
?57 ???????????? {
?58 ???????????????? get
?59 ???????????????? {
?60 ???????????????????? return ?NonStaticIntField;
?61 ????????????????}
?62 ???????????????? set
?63 ???????????????? {
?64 ????????????????????NonStaticIntField? = ?value;
?65 ????????????????}
?66 ????????????}
?67 ????????}
?68
?69 ???????? public ? class ?UnitTest
?70 ???????? {
?71 ???????????? private ? static ?DynamicMethodFactory?fac? = ? new ?DynamicMethodFactory();
?72
?73 ???????????? public ? static ? void ?TestStaticMethod()
?74 ???????????? {
?75 ????????????????StaticDynamicMethodProxyHandler?handler? = ?fac.GetStaticMethodDelegate( typeof (TestClass).GetMethod( " StaticReturnVoidMethod " ));
?76 ????????????????handler( null );
?77
?78 ???????????????? object []?inputParams? = ? new ? object []? {? " str " ,? 1 ,? 3 ,? " instr " ?} ;
?79 ????????????????handler? = ?fac.GetStaticMethodDelegate( typeof (TestClass).GetMethod( " StaticReturnIntMethod " ));
?80 ???????????????? object ?ret? = ?handler(inputParams);
?81 ????????????????Check.Assert((( int )inputParams[ 2 ])? == ? 2 );
?82 ????????????????Check.Assert((( string )inputParams[ 3 ])? == ? " refstr " );
?83 ????????????????Check.Assert((( int )ret)? == ? 4 );
?84 ????????????}
?85
?86 ???????????? public ? static ? void ?TestStaticField()
?87 ???????????? {
?88 ????????????????TestClass.StaticIntField? = ? - 1 ;
?89 ????????????????FieldInfo?field? = ? typeof (TestClass).GetField( " StaticIntField " );?;
?90 ????????????????StaticDynamicMethodProxyHandler?handler? = ?fac.GetStaticFieldSetDelegate(field);
?91 ????????????????handler( new ? object []? {? 5 ?} );
?92 ????????????????Check.Assert(TestClass.StaticIntField? == ? 5 );
?93 ????????????????handler? = ?fac.GetStaticFieldGetDelegate(field);
?94 ????????????????Check.Assert((( int )handler( null ))? == ? 5 );
?95 ????????????}
?96
?97 ???????????? public ? static ? void ?TestStaticProperty()
?98 ???????????? {
?99 ????????????????TestClass.StaticIntField? = ? - 1 ;
100 ????????????????PropertyInfo?property? = ? typeof (TestClass).GetProperty( " StaticIntProperty " );?;
101 ????????????????StaticDynamicMethodProxyHandler?handler? = ?fac.GetStaticMethodDelegate(property.GetSetMethod());
102 ????????????????handler( new ? object []? {? 5 ?} );
103 ????????????????Check.Assert(TestClass.StaticIntProperty? == ? 5 );
104 ????????????????handler? = ?fac.GetStaticMethodDelegate(property.GetGetMethod());
105 ????????????????Check.Assert((( int )handler( null ))? == ? 5 );
106 ????????????}
107
108 ???????????? public ? static ? void ?TestNonStaticMethod()
109 ???????????? {
110 ????????????????TestClass?obj? = ? new ?TestClass();
111
112 ????????????????DynamicMethodProxyHandler?handler? = ?fac.GetMethodDelegate( typeof (TestClass).GetMethod( " NonStaticReturnVoidMethod " ));
113 ????????????????handler(obj,? null );
114
115 ???????????????? object []?inputParams? = ? new ? object []? {? " str " ,? 1 ,? null ,? null ?} ;
116 ????????????????handler? = ?fac.GetMethodDelegate( typeof (TestClass).GetMethod( " NonStaticReturnIntMethod " ));
117 ???????????????? object ?ret? = ?handler(obj,?inputParams);
118 ????????????????Check.Assert((( int )inputParams[ 2 ])? == ? 2 );
119 ????????????????Check.Assert((( string )inputParams[ 3 ])? == ? " outstr " );
120 ????????????????Check.Assert((( int )ret)? == ? 3 );
121 ????????????}
122
123 ???????????? public ? static ? void ?TestNonStaticField()
124 ???????????? {
125 ????????????????TestClass?obj? = ? new ?TestClass();
126 ????????????????obj.NonStaticIntField? = ? - 1 ;
127
128 ????????????????FieldInfo?field? = ? typeof (TestClass).GetField( " NonStaticIntField " );?;
129 ????????????????DynamicMethodProxyHandler?handler? = ?fac.GetFieldSetDelegate(field);
130 ????????????????handler(obj,? new ? object []? {? 5 ?} );
131 ????????????????Check.Assert(obj.NonStaticIntField? == ? 5 );
132 ????????????????handler? = ?fac.GetFieldGetDelegate(field);
133 ????????????????Check.Assert((( int )handler(obj,? null ))? == ? 5 );
134 ????????????}
135
136 ???????????? public ? static ? void ?TestNonStaticProperty()
137 ???????????? {
138 ????????????????TestClass?obj? = ? new ?TestClass();
139 ????????????????obj.NonStaticIntField? = ? - 1 ;
140
141 ????????????????PropertyInfo?property? = ? typeof (TestClass).GetProperty( " NonStaticIntProperty " );?;
142 ????????????????DynamicMethodProxyHandler?handler? = ?fac.GetMethodDelegate(property.GetSetMethod());
143 ????????????????handler(obj,? new ? object []? {? 5 ?} );
144 ????????????????Check.Assert(obj.NonStaticIntField? == ? 5 );
145 ????????????????handler? = ?fac.GetMethodDelegate(property.GetGetMethod());
146 ????????????????Check.Assert((( int )handler(obj,? null ))? == ? 5 );
147 ????????????}
148 ????????}
149 ????}

DynamicMethodFactory類還可以用于以非泛型方法的調用語法調用泛型方法，在之前的一篇文章介紹過，這里就不重復了，感興趣的朋友可以參見： 改進的 以非泛型方式調用泛型方法”之基于DynamicMethod的實現 。

有任何問題歡迎回復討論。

//The End

基于CodeGenerator的Emit代碼生成輔助類源碼及演示