This documentation is archived and is not being maintained.

ConstructorBuilder Class

Defines and represents a constructor of a dynamic class.

For a list of all members of this type, see ConstructorBuilder Members.

System.Object
   System.Reflection.MemberInfo
      System.Reflection.MethodBase
         System.Reflection.ConstructorInfo
            System.Reflection.Emit.ConstructorBuilder

[Visual Basic]
NotInheritable Public Class ConstructorBuilder
   Inherits ConstructorInfo
[C#]
public sealed class ConstructorBuilder : ConstructorInfo
[C++]
public __gc __sealed class ConstructorBuilder : public
   ConstructorInfo
[JScript]
public class ConstructorBuilder extends ConstructorInfo

Thread Safety

Reflection Emit is thread-safe when using assemblies that were created with the AppDomain.DefineDynamicAssembly method with the Boolean parameter isSynchronized set to true.

Remarks

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 illustates the contextual usage of a ConstructorBuilder.

[Visual Basic] 

Imports System
Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit

 _

Class TestCtorBuilder
   
   
   Public Shared Function DynamicPointTypeGen() As Type
      
      Dim pointType As Type = Nothing
      Dim ctorParams() As Type = {GetType(Integer), GetType(Integer), GetType(Integer)}
      
      Dim myDomain As AppDomain = Thread.GetDomain()
      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyDynamicAssembly"
      
      Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, AssemblyBuilderAccess.RunAndSave)
      
      Dim pointModule As ModuleBuilder = myAsmBuilder.DefineDynamicModule("PointModule", "Point.dll")
      
      Dim pointTypeBld As TypeBuilder = pointModule.DefineType("Point", TypeAttributes.Public)
      
      Dim xField As FieldBuilder = pointTypeBld.DefineField("x", GetType(Integer), FieldAttributes.Public)
      Dim yField As FieldBuilder = pointTypeBld.DefineField("y", GetType(Integer), FieldAttributes.Public)
      Dim zField As FieldBuilder = pointTypeBld.DefineField("z", GetType(Integer), FieldAttributes.Public)
      
      Dim objType As Type = Type.GetType("System.Object")
      Dim objCtor As ConstructorInfo = objType.GetConstructor(New Type() {})
      
      Dim pointCtor As ConstructorBuilder = pointTypeBld.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, ctorParams)
      Dim ctorIL As ILGenerator = 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.
      Dim mthdNames() As String = {"GetX", "GetY", "GetZ"}
      
      Dim mthdName As String
      For Each mthdName In  mthdNames
         Dim getFieldMthd As MethodBuilder = pointTypeBld.DefineMethod(mthdName, MethodAttributes.Public, GetType(Integer), Nothing)
         Dim mthdIL As ILGenerator = getFieldMthd.GetILGenerator()
         
         mthdIL.Emit(OpCodes.Ldarg_0)
         Select Case mthdName
            Case "GetX"
               mthdIL.Emit(OpCodes.Ldfld, xField)
            Case "GetY"
               mthdIL.Emit(OpCodes.Ldfld, yField)
            Case "GetZ"
               mthdIL.Emit(OpCodes.Ldfld, zField)
         End Select
         
         mthdIL.Emit(OpCodes.Ret)
      Next mthdName 
      ' Finally, we create the type.
      pointType = pointTypeBld.CreateType()
      
      ' Let's save it, just for posterity.
      myAsmBuilder.Save("Point.dll")
      
      Return pointType
   End Function 'DynamicPointTypeGen
    
   
   Public Shared Sub Main()
      
      Dim myDynamicType As Type = Nothing
      Dim aPoint As Object = Nothing
      Dim aPtypes() As Type = {GetType(Integer), GetType(Integer), GetType(Integer)}
      Dim aPargs() As 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: ")
      Dim member As MemberInfo
      For Each member In  myDynamicType.GetMembers()
         Console.WriteLine("-- {0} {1};", member.MemberType, member.Name)
      Next member
      
      Console.WriteLine("---")
      
      ' Let's take a look at the constructor we created.
      Dim myDTctor As ConstructorInfo = 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, Nothing, aPoint, New Object() {}))
      Console.WriteLine("aPoint.y = {0}", myDynamicType.InvokeMember("GetY", BindingFlags.InvokeMethod, Nothing, aPoint, New Object() {}))
      Console.WriteLine("aPoint.z = {0}", myDynamicType.InvokeMember("GetZ", BindingFlags.InvokeMethod, Nothing, aPoint, New Object() {}))
   End Sub 'Main
End Class 'TestCtorBuilder



' +++ 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


[C#] 

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
        
    }
    
}


[C++] 

#using <mscorlib.dll>

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;

Type* DynamicPointTypeGen() {

   Type* pointType = 0;
   Type* temp0 [] = {__typeof(int),
      __typeof(int),
      __typeof(int)};

   Type* ctorParams[] = temp0;

   AppDomain*  myDomain = Thread::GetDomain();
   AssemblyName* myAsmName = new AssemblyName();
   myAsmName->Name = S"MyDynamicAssembly";

   AssemblyBuilder*  myAsmBuilder = myDomain->DefineDynamicAssembly(myAsmName,
      AssemblyBuilderAccess::RunAndSave);

   ModuleBuilder*  pointModule = myAsmBuilder->DefineDynamicModule(S"PointModule",
      S"Point.dll");

   TypeBuilder*  pointTypeBld = pointModule->DefineType(S"Point",
      TypeAttributes::Public);

   FieldBuilder*  xField = pointTypeBld->DefineField(S"x", __typeof(int),
      FieldAttributes::Public);
   FieldBuilder*  yField = pointTypeBld->DefineField(S"y", __typeof(int),
      FieldAttributes::Public);
   FieldBuilder*  zField = pointTypeBld->DefineField(S"z", __typeof(int),
      FieldAttributes::Public);


   Type*  objType = Type::GetType(S"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 bject 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 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* temp1 [] = {S"GetX", S"GetY", S"GetZ"};
   String* mthdNames[] = temp1;

   System::Collections::IEnumerator* myEnum = mthdNames->GetEnumerator();
   while (myEnum->MoveNext()) {
      String* mthdName = __try_cast<String*>(myEnum->Current);

      MethodBuilder*  getFieldMthd = pointTypeBld->DefineMethod(mthdName,
         MethodAttributes::Public,
         __typeof(int),
         0);
      ILGenerator*  mthdIL = getFieldMthd->GetILGenerator();

      mthdIL->Emit(OpCodes::Ldarg_0);

      if( mthdName->Equals(S"GetX") ) mthdIL->Emit(OpCodes::Ldfld, xField);
      else if( mthdName->Equals(S"GetY") ) mthdIL->Emit(OpCodes::Ldfld, yField);
      else if( mthdName->Equals(S"GetZ") ) mthdIL->Emit(OpCodes::Ldfld, zField);
      mthdIL->Emit(OpCodes::Ret);

   }
   // Finally, we create the type.

   pointType = pointTypeBld->CreateType();

   // Let's save it, just for posterity.

   myAsmBuilder->Save(S"Point.dll");

   return pointType;
}

int main() {

   Type* myDynamicType = 0;
   Object* aPoint = 0;

   Type* temp2 [] = {__typeof(int), __typeof(int), __typeof(int)};
   Type* aPtypes[] = temp2;

   Object* temp3 [] = {__box(4), __box(5), __box(6)};
   Object* aPargs[] = temp3;

   // Call the  method to build our dynamic class.

   myDynamicType = DynamicPointTypeGen();

   Console::WriteLine(S"Some information about my new Type '{0}':",
      myDynamicType->FullName);
   Console::WriteLine(S"Assembly: '{0}'", myDynamicType->Assembly);
   Console::WriteLine(S"Attributes: '{0}'", __box(myDynamicType->Attributes));
   Console::WriteLine(S"Module: '{0}'", myDynamicType->Module);
   Console::WriteLine(S"Members: ");
   System::Collections::IEnumerator* myEnum = myDynamicType->GetMembers()->GetEnumerator();
   while (myEnum->MoveNext()) {
      MemberInfo* member = __try_cast<MemberInfo*>(myEnum->Current);
      Console::WriteLine(S"-- {0} {1};", __box(member->MemberType), member->Name);
   }

   Console::WriteLine(S"---");

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

   ConstructorInfo*  myDTctor = myDynamicType->GetConstructor(aPtypes);
   Console::WriteLine(S"Constructor: {0};", myDTctor);

   Console::WriteLine(S"---");

   // Now, we get to use our dynamically-created class by invoking the constructor.

   aPoint = myDTctor->Invoke(aPargs);
   Console::WriteLine(S"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(S"aPoint.x = {0}",
      myDynamicType->InvokeMember(S"GetX",
      BindingFlags::InvokeMethod,
      0,
      aPoint,
      new Object*[0]));
   Console::WriteLine(S"aPoint.y = {0}",
      myDynamicType->InvokeMember(S"GetY",
      BindingFlags::InvokeMethod,
      0,
      aPoint,
      new Object*[0]));
   Console::WriteLine(S"aPoint.z = {0}",
      myDynamicType->InvokeMember(S"GetZ",
      BindingFlags::InvokeMethod,
      0,
      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
}

Requirements

Namespace: System.Reflection.Emit

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

See Also

ConstructorBuilder Members | System.Reflection.Emit Namespace

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