ConstructorBuilder.GetILGenerator Method

Definition

Namespace:

System.Reflection.Emit

Assemblies:

netstandard.dll, System.Reflection.Emit.dll

Gets an ILGenerator that can be used to emit a method body for this constructor.

Overloads

GetILGenerator(Int32)	Gets an ILGenerator object, with the specified MSIL stream size, that can be used to build a method body for this constructor.
GetILGenerator()	Gets an ILGenerator for this constructor.

GetILGenerator(Int32)

Source:

ConstructorBuilder.cs

Gets an ILGenerator object, with the specified MSIL stream size, that can be used to build a method body for this constructor.

C#

public System.Reflection.Emit.ILGenerator GetILGenerator(int streamSize);

Parameters

streamSize

Int32

The size of the MSIL stream, in bytes.

Returns

ILGenerator

An ILGenerator for this constructor.

Exceptions

InvalidOperationException

The constructor is a parameterless constructor.

-or-

The constructor has MethodAttributes or MethodImplAttributes flags indicating that it should not have a method body.

Remarks

The runtime generates the code for default constructors. Therefore, if an attempt is made to obtain an ILGenerator for a parameterless constructor, an exception is thrown.

GetILGenerator()

Source:

ConstructorBuilder.cs

Gets an ILGenerator for this constructor.

C#

public System.Reflection.Emit.ILGenerator GetILGenerator();

Returns

ILGenerator

An ILGenerator object for this constructor.

Exceptions

InvalidOperationException

The constructor is a parameterless constructor.

-or-

The constructor has MethodAttributes or MethodImplAttributes flags indicating that it should not have a method body.

Examples

The following code sample illustrates the use of the GetILGenerator method.

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
    }
}

Remarks

The runtime generates the code for default constructors. Therefore, if an attempt is made to obtain an ILGenerator, an exception will be thrown.