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ConstructorBuilder Class

Defines and represents a constructor of a dynamic class.

Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)

[ClassInterfaceAttribute(ClassInterfaceType.None)] 
[ComVisibleAttribute(true)] 
public sealed class ConstructorBuilder : ConstructorInfo, _ConstructorBuilder
/** @attribute ClassInterfaceAttribute(ClassInterfaceType.None) */ 
/** @attribute ComVisibleAttribute(true) */ 
public final class ConstructorBuilder extends ConstructorInfo implements _ConstructorBuilder
ClassInterfaceAttribute(ClassInterfaceType.None) 
ComVisibleAttribute(true) 
public final class ConstructorBuilder extends ConstructorInfo implements _ConstructorBuilder
Not applicable.

ConstructorBuilder is used to fully describe a constructor in Microsoft intermediate language (MSIL), including the name, attributes, signature, and constructor body. It is used in conjunction with the TypeBuilder class to create classes at run time. Call DefineConstructor to get an instance of ConstructorBuilder.

The following code sample illustrates the contextual usage of a ConstructorBuilder.


using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

class TestCtorBuilder {
 
  	public static Type DynamicPointTypeGen() {
	  
	   Type pointType = null;
	   Type[] ctorParams = new Type[] {typeof(int),
					    typeof(int),
					    typeof(int)};
 	
	   AppDomain myDomain = Thread.GetDomain();
	   AssemblyName myAsmName = new AssemblyName();
	   myAsmName.Name = "MyDynamicAssembly";
	
	   AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
					  myAsmName, 
					  AssemblyBuilderAccess.RunAndSave);

   	   ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
									"Point.dll");

	   TypeBuilder pointTypeBld = pointModule.DefineType("Point",
						              TypeAttributes.Public);

	   FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                          FieldAttributes.Public);
	   FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int), 
                                                          FieldAttributes.Public);
	   FieldBuilder zField = pointTypeBld.DefineField("z", typeof(int),
                                                          FieldAttributes.Public);


           Type objType = Type.GetType("System.Object"); 
           ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);

	   ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
					  MethodAttributes.Public,
					  CallingConventions.Standard,
					  ctorParams);
	   ILGenerator ctorIL = pointCtor.GetILGenerator();

	   // NOTE: ldarg.0 holds the "this" reference - ldarg.1, ldarg.2, and ldarg.3
	   // hold the actual passed parameters. ldarg.0 is used by instance methods
	   // to hold a reference to the current calling object instance. Static methods
	   // do not use arg.0, since they are not instantiated and hence no reference
	   // is needed to distinguish them. 

           ctorIL.Emit(OpCodes.Ldarg_0);

	   // Here, we wish to create an instance of System.Object by invoking its
  	   // constructor, as specified above.

           ctorIL.Emit(OpCodes.Call, objCtor);

	   // Now, we'll load the current instance ref in arg 0, along
	   // with the value of parameter "x" stored in arg 1, into stfld.

           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_1);
           ctorIL.Emit(OpCodes.Stfld, xField); 

	   // Now, we store arg 2 "y" in the current instance with stfld.

           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_2);
           ctorIL.Emit(OpCodes.Stfld, yField); 

	   // Last of all, arg 3 "z" gets stored in the current instance.

           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_3);
           ctorIL.Emit(OpCodes.Stfld, zField); 
           
           // Our work complete, we return.

	   ctorIL.Emit(OpCodes.Ret); 

	   // Now, let's create three very simple methods so we can see our fields.

	   string[] mthdNames = new string[] {"GetX", "GetY", "GetZ"}; 

           foreach (string mthdName in mthdNames) {
              MethodBuilder getFieldMthd = pointTypeBld.DefineMethod(
				           mthdName, 
				           MethodAttributes.Public,
                                           typeof(int), 
                                           null);
	      ILGenerator mthdIL = getFieldMthd.GetILGenerator();
	   
	      mthdIL.Emit(OpCodes.Ldarg_0);
  	      switch (mthdName) {
	         case "GetX": mthdIL.Emit(OpCodes.Ldfld, xField);
			      break;
	         case "GetY": mthdIL.Emit(OpCodes.Ldfld, yField);
			      break;
	         case "GetZ": mthdIL.Emit(OpCodes.Ldfld, zField);
			      break;

	      }
	      mthdIL.Emit(OpCodes.Ret);

           }
	   // Finally, we create the type.

 	   pointType = pointTypeBld.CreateType();

	   // Let's save it, just for posterity.
	   
	   myAsmBuilder.Save("Point.dll");
	
	   return pointType;

 	}

	public static void Main() {
	
	   Type myDynamicType = null;
           object aPoint = null;
	   Type[] aPtypes = new Type[] {typeof(int), typeof(int), typeof(int)};
           object[] aPargs = new object[] {4, 5, 6};
	
	   // Call the  method to build our dynamic class.

	   myDynamicType = DynamicPointTypeGen();

	   Console.WriteLine("Some information about my new Type '{0}':",
			      myDynamicType.FullName);
	   Console.WriteLine("Assembly: '{0}'", myDynamicType.Assembly);
	   Console.WriteLine("Attributes: '{0}'", myDynamicType.Attributes);
	   Console.WriteLine("Module: '{0}'", myDynamicType.Module);
	   Console.WriteLine("Members: "); 
	   foreach (MemberInfo member in myDynamicType.GetMembers()) {
		Console.WriteLine("-- {0} {1};", member.MemberType, member.Name);
	   }

           Console.WriteLine("---");

	   // Let's take a look at the constructor we created.

	   ConstructorInfo myDTctor = myDynamicType.GetConstructor(aPtypes);
           Console.WriteLine("Constructor: {0};", myDTctor.ToString());

           Console.WriteLine("---");
	  
           // Now, we get to use our dynamically-created class by invoking the constructor. 

	   aPoint = myDTctor.Invoke(aPargs);
           Console.WriteLine("aPoint is type {0}.", aPoint.GetType());
	   	   

	   // Finally, let's reflect on the instance of our new type - aPoint - and
	   // make sure everything proceeded according to plan.

	   Console.WriteLine("aPoint.x = {0}",
			     myDynamicType.InvokeMember("GetX",
						        BindingFlags.InvokeMethod,
							null,
							aPoint,
							new object[0]));
	   Console.WriteLine("aPoint.y = {0}",
			     myDynamicType.InvokeMember("GetY",
						        BindingFlags.InvokeMethod,
							null,
							aPoint,
							new object[0]));
	   Console.WriteLine("aPoint.z = {0}",
			     myDynamicType.InvokeMember("GetZ",
						        BindingFlags.InvokeMethod,
							null,
							aPoint,
							new object[0]));

	    

	   // +++ OUTPUT +++
	   // Some information about my new Type 'Point':
	   // Assembly: 'MyDynamicAssembly, Version=0.0.0.0'
	   // Attributes: 'AutoLayout, AnsiClass, NotPublic, Public'
	   // Module: 'PointModule'
	   // Members: 
	   // -- Field x;
	   // -- Field y;
	   // -- Field z;
           // -- Method GetHashCode;
           // -- Method Equals;
           // -- Method ToString;
           // -- Method GetType;
           // -- Constructor .ctor;
	   // ---
	   // Constructor: Void .ctor(Int32, Int32, Int32);
	   // ---
	   // aPoint is type Point.
	   // aPoint.x = 4
	   // aPoint.y = 5
	   // aPoint.z = 6
	    
	}
    
}


System.Object
   System.Reflection.MemberInfo
     System.Reflection.MethodBase
       System.Reflection.ConstructorInfo
        System.Reflection.Emit.ConstructorBuilder
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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