C # uses emit to build constructors and properties

Suppose we need a class named Kitty, which is under the Pets assembly.

1     //Specify a new assembly name 2     var assemblyname = new AssemblyName ("Pets"); 3  4     //CREATE Assembly Bui Lder 5     var assemblybuilder = Appdomain.currentdomain 6       . DefineDynamicAssembly (AssemblyName, Assemblybuilderaccess.runandsave); 7  8     //Create Module Builder 9     var modulebuilder = assemblybuilder.definedynamicmodule ("Petsmodule", " Pets.dll ")     //Create Type builder for a class12     var typeBuilder = Modulebuilder.definetype (" Kitty ", TypeA Ttributes. public);

Defining fields

The Kitty class consists of two private fields _id and _name. Defined with a type constructor,

1     var fieldid = Typebuilder.definefield (2       "_id", typeof (int), fieldattributes.private); 3     var fieldName = Typebuilder.definefield (4       "_name", typeof (String), fieldattributes.private);

Defining constructors

The Kitty class contains a constructor with two parameters, one for the integer ID, and the string name for the parameter. constructor, assign the parameter ID to the private field _id, assign the parameter name to the private field _name,

1     Type objType = Type.GetType ("System.Object"); 2     ConstructorInfo objctor = objtype.getconstructor (new type[0] ); 3  4     type[] Constructorargs = {typeof (int), typeof (String)}; 5  6     var constructorbuilder = Typebuilder.defineconstructor (7         methodattributes.public, Callingconventions.standard, ConstructorArgs); 8     ILGenerator ilofctor = Constructorbuilder.getilgenerator (); 9     ilofctor.emit (OPCODES.LDARG_0);     Ilofctor.emit (Opcodes.call, objctor);     ilofctor.emit (OPCODES.LDARG_0);     Ilofctor.emit (Opcodes.ldarg _1),     ilofctor.emit (OPCODES.STFLD, FieldID), Ilofctor.emit (     opcodes.ldarg_0), Ilofctor.emit     ( opcodes.ldarg_2);     ilofctor.emit (OPCODES.STFLD, fieldName); 18     

Defining properties

Create ID and name two properties for the Kitty class, read and set private fields _id and _name. The properties in C # define getter and setter two methods respectively.

 1 var methodgetid = Typebuilder.definemethod (2 "GetId", Methodattributes.public, typeof (int), NULL);  3 var Methodsetid = Typebuilder.definemethod (4 "SetId", methodattributes.public, NULL, new type[] {typeof (int) }); 5 6 var Ilofgetid = Methodgetid.getilgenerator (); 7 Ilofgetid.emit (OPCODES.LDARG_0); This 8 ilofgetid.emit (OPCODES.LDFLD, FieldID); 9 Ilofgetid.emit (Opcodes.ret); var ilofsetid = Methodsetid.getilgenerator (); Ilofsetid.emit (Opcodes.lda RG_0); This13 Ilofsetid.emit (opcodes.ldarg_1);     The first one in arguments list14 ilofsetid.emit (OPCODES.STFLD, FieldID); Ilofsetid.emit (Opcodes.ret); 16 17 Create ID property18 var PropertyId = Typebuilder.defineproperty ("Id", Propertyattributes.none, typeof ( int), NULL); Propertyid.setgetmethod (Methodgetid); Propertyid.setsetmethod (Methodsetid); var Methodge Tname = Typebuilder.definemethod ("GetName", MethodAttributes.Public, typeof (String), null), var methodsetname = Typebuilder.definemethod ("SetName", methodattributes.pub LIC, NULL, new type[] {typeof (String)}); var ilofgetname = Methodgetname.getilgenerator (); Ilofgetname.em It (OPCODES.LDARG_0); This30 Ilofgetname.emit (OPCODES.LDFLD, fieldName); Ilofgetname.emit (Opcodes.ret); + var ilofsetname = Methodsetname.getilgenerator (); Ilofsetname.emit (OPCODES.LDARG_0); This35 Ilofsetname.emit (opcodes.ldarg_1); The first one in arguments list36 ilofsetname.emit (OPCODES.STFLD, fieldName); Panax Notoginseng Ilofsetname.emit (Opcodes.ret); 3 8//Create Name property40 var propertyname = Typebuilder.defineproperty ("name", PROPERTYATTRIBUTES.N One, typeof (String), null); Propertyname.setgetmethod (methodgetname); Propertyname.setsetmethod (Methodsetname) ;

Defining methods

Adds a ToString () method to the Kitty class, returning a string value.

 1//Create ToString () Method 2 var methodtostring = Typebuilder.definemethod (3 "ToString", 4 method attributes.virtual | Methodattributes.public, 5 typeof (String), 6 null); 7 8 var iloftostring = Methodtostring.getilgenerator (); 9 var local = iloftostring.declarelocal (typeof (String)); Create a local Variable10 iloftostring.emit (Opcodes.ldstr, "id:[{0}], name:[{1}]"); Iloftostring.emit (opcodes . LDARG_0); THIS12 Iloftostring.emit (OPCODES.LDFLD, FieldID); Iloftostring.emit (Opcodes.box, typeof (int)); Boxing the value type to object14 iloftostring.emit (OPCODES.LDARG_0); This15 Iloftostring.emit (OPCODES.LDFLD, fieldName); Iloftostring.emit (opcodes.call,17 typeof (String). GetMethod ("Format", new type[] {typeof (String), typeof (Object), typeof (Object)}), Iloftostring.emit (opcod Es. Stloc, local); Set local Variable20 iloftostring.emit (opcodes.ldloc, local); Load local variable to stack21 iloftostring.emit (opcodes.ret); 

Save Type

Build the type and save the assembly to the Pets.dll file.

1     /Then create the whole class type2     var ClassType = TypeBuilder.CreateType (); 3 4     //save Assembly5     Asse Mblybuilder.save ("Pets.dll");

Anti-compilation class

Use the anti-compiler to view the generated classes,

1 using System; 2 public class Kitty 3 {4   private int _id; 5   private string _name; 6 public   int ID 7   {8     get 9     {Ten       return this._id;11     }12     set13     {       this._id = value;15}16   }17   Public String Name18   {     get20     {       this._name;22     }23     set24     {       this._ Name = value;26     }27   }28 public   Kitty (int ID, string name)   {     this._id = id;31     this._ Name = name;32   }33 public   override string ToString ()   . {A     return string. Format ("id:[{0}], name:[{1}]", this._id, This._name);   }37}

Full code

  1 using System;  2 using System.Reflection;  3 using System.Reflection.Emit;       4 5 Namespace Emitcreatemembers 6 {7 Class program 8 {9 static void Main (string[] args) 10 {11 Specify a new assembly name of var assemblyname = new AssemblyName ("Pets"); //CREATE Assembly builder for var AssemblyBuilder = Appdomain.currentdomain 16. DefineDynamicAssembly (AssemblyName, Assemblybuilderaccess.runandsave); +//Create module builder var ModuleBuilder = AssemblyBuilder.DefineDynamicModule ("Petsmodule", "Pets . dll "); //Create Type Builder for a class of var typeBuilder = Modulebuilder.definetype ("Kitty", Typeattribute S.public); */Then create whole class structure createkittyclassstructure (TypeBuilder); +/Then create the whole class type-var ClassType = TypeBuilder.CreateType (); +//Save assembly to Assemblybuilder.save ("Pets.dll");Console.WriteLine ("Hi, Dennis, a Pets assembly have been generated for you."); Console.ReadLine (); Createkittyclassstructure (TypeBuilder TypeBuilder) ($//----Defin  E fields----FieldID var = typebuilder.definefield ("_id", typeof (int), fieldattributes.private); var fieldName = Typebuilder.definefield ("_name", typeof (String), fieldattributes.private); Define//----costructors-----Type ObjType = Type.GetType ("System.Object"); ConstructorInfo objctor = Objtype.getconstructor (new type[0]); Type[] Constructorargs = {typeof (int), typeof (String)}; ConstructorBuilder var = typebuilder.defineconstructor (Methodattributes.public, Callingconventio Ns. Standard, Constructorargs); ILGenerator ilofctor = Constructorbuilder.getilgenerator (); Ilofctor.emit (OPCODES.LDARG_0);       58Ilofctor.emit (Opcodes.call, objctor); Ilofctor.emit (OPCODES.LDARG_0); Ilofctor.emit (opcodes.ldarg_1); Ilofctor.emit (OPCODES.STFLD, FieldID); Ilofctor.emit (OPCODES.LDARG_0); Ilofctor.emit (opcodes.ldarg_2); Ilofctor.emit (OPCODES.STFLD, fieldName); Ilofctor.emit (Opcodes.ret); //----Define properties----Methodgetid = Typebuilder.definemethod ("GetId", M Ethodattributes.public, typeof (int), NULL); Methodsetid var = typebuilder.definemethod ("SetId", methodattributes.public, NULL, new type[] {TYPEO f (int)}); The Ilofgetid var = methodgetid.getilgenerator (); Ilofgetid.emit (OPCODES.LDARG_0); This ilofgetid.emit (OPCODES.LDFLD, FieldID); Ilofgetid.emit (Opcodes.ret); Ilofsetid var = methodsetid.getilgenerator (); Ilofsetid.emit (OPCODES.LDARG_0); This is Bayi ilofsetid.emit (opcodes.ldarg_1); The first oneIn arguments list Ilofsetid.emit (OPCODES.STFLD, FieldID); Ilofsetid.emit (Opcodes.ret); //Create ID Property--var PropertyId = Typebuilder.defineproperty ("id", propertyattribut Es. None, typeof (int), NULL); Propertyid.setgetmethod (Methodgetid); Propertyid.setsetmethod (Methodsetid); methodgetname var = typebuilder.definemethod ("GetName", Methodattributes.public, typeof (String), NULL); methodsetname var = typebuilder.definemethod (94 "SetName", methodattributes.public, NULL, new type[] {T Ypeof (String)}); ilofgetname var = methodgetname.getilgenerator (); Ilofgetname.emit (OPCODES.LDARG_0); This 98 ilofgetname.emit (OPCODES.LDFLD, fieldName); Ilofgetname.emit (Opcodes.ret), 101 var ilofsetname = Methodsetname.getilgenerator (); 102 Ilofsetnam E.emit (OPCODES.LDARG_0); this103 Ilofsetname.emit (opcodes.ldarg_1); The First ONE in Arguments list104 ilofsetname.emit (OPCODES.STFLD, fieldName); Ilofsetname.emit (Opcodes.ret); 106 107 Create Name property108 var propertyname = Typebuilder.defineproperty (109 "Name", PropertyAttributes . None, typeof (String), null); Propertyname.setgetmethod (methodgetname); 111 Propertyname.setsetmethod (MethodS Etname) 113//----Define methods----//Create ToString () method116 var methodtostring = t Ypebuilder.definemethod (117 "ToString", 118 methodattributes.virtual | methodattributes.public,119 typeof (String), (null), 121 122 var iloftostring = Methodtostring.getil Generator (); 123 var local = Iloftostring.declarelocal (typeof (String)); Create a local variable124 iloftostring.emit (Opcodes.ldstr, "id:[{0}], name:[{1}]"), Iloftostring.emit (O PCODES.LDARG_0); this126 Iloftostring.emit (OPCODES.LDFLD, FieldID); 127 Iloftostring.emit (Opcodes.box, typeof (int)); Boxing the value type to object128 iloftostring.emit (OPCODES.LDARG_0); this129 Iloftostring.emit (OPCODES.LDFLD, FieldName), (Iloftostring.emit opcodes.call,131 (s Tring). GetMethod ("Format", new type[] {typeof (String), typeof (Object), typeof (Object)}); 133 Iloftostring.emit (Opcodes.stloc, local); Set local variable134 iloftostring.emit (opcodes.ldloc, local); Load local variable to stack135 iloftostring.emit (Opcodes.ret); 136}137}138}

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Learn more about using emit to construct dynamic proxy classes

C # uses emit to build constructors and properties