static void DynamicCreateMethod()
{
// Create an array that specifies the types of the parameters
// of the dynamic method. This dynamic method has a String
// parameter and an Integer parameter.
Type[] helloArgs = { typeof(string), typeof(int) };
// Create a dynamic method with the name "Hello", a return type
// of Integer, and two parameters whose types are specified by
// the array helloArgs. Create the method in the module that
// defines the String class.
DynamicMethod hello = new DynamicMethod("Hello",
typeof(int),
helloArgs,
typeof(string).Module);
// Create an array that specifies the parameter types of the
// overload of Console.WriteLine to be used in Hello.
Type[] writeStringArgs = { typeof(string) };
// Get the overload of Console.WriteLine that has one String parameter.
MethodInfo writeString = typeof(Console).GetMethod("WriteLine", writeStringArgs);
// Get an ILGenerator and emit a body for the dynamic method,
// using a stream size larger than the IL that will be emitted.
ILGenerator il = hello.GetILGenerator(256);
// Load the first argument, which is a string, onto the stack.
il.Emit(OpCodes.Ldarg_0);
// Call the overload of Console.WriteLine that prints a string.
il.EmitCall(OpCodes.Call, writeString, null);
// The Hello method returns the value of the second argument;
// to do this, load the onto the stack and return.
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Ret);
// Display MethodAttributes for the dynamic method, set when
// the dynamic method was created.
Console.WriteLine("\r\nMethod Attributes: {0}", hello.Attributes);
// Display the calling convention of the dynamic method, set when the dynamic method was created.
Console.WriteLine("\r\nCalling convention: {0}", hello.CallingConvention);
// Display the declaring type, which is always null for dynamic methods.
if (hello.DeclaringType == null)
Console.WriteLine("\r\nDeclaringType is always null for dynamic methods.");
else
Console.WriteLine("DeclaringType: {0}", hello.DeclaringType);
// Display the default value for InitLocals.
if (hello.InitLocals)
Console.Write("\r\nThis method contains verifiable code.");
else
Console.Write("\r\nThis method contains unverifiable code.");
Console.WriteLine(" (InitLocals = {0})", hello.InitLocals);
// Display the module specified when the dynamic method was created.
Console.WriteLine("\r\nModule: {0}", hello.Module);
// Display the name specified when the dynamic method was created.
// Note that the name can be blank.
Console.WriteLine("\r\nName: {0}", hello.Name);
// For dynamic methods, the reflected type is always null.
if (hello.ReflectedType == null)
Console.WriteLine("\r\nReflectedType is null.");
else
Console.WriteLine("\r\nReflectedType: {0}", hello.ReflectedType);
if (hello.ReturnParameter == null)
Console.WriteLine("\r\nMethod has no return parameter.");
else
Console.WriteLine("\r\nReturn parameter: {0}", hello.ReturnParameter);
// If the method has no return type, ReturnType is System.Void.
Console.WriteLine("\r\nReturn type: {0}", hello.ReturnType);
// ReturnTypeCustomAttributes returns an ICustomeAttributeProvider
// that can be used to enumerate the custom attributes of the
// return value. At present, there is no way to set such custom
// attributes, so the list is empty.
if (hello.ReturnType == typeof(void))
Console.WriteLine("The method has no return type.");
else
{
ICustomAttributeProvider caProvider = hello.ReturnTypeCustomAttributes;
object[] returnAttributes = caProvider.GetCustomAttributes(true);
if (returnAttributes.Length == 0)
Console.WriteLine("\r\nThe return type has no custom attributes.");
else
{
Console.WriteLine("\r\nThe return type has the following custom attributes:");
foreach (object attr in returnAttributes)
{
Console.WriteLine("\t{0}", attr.ToString());
}
}
}
Console.WriteLine("\r\nToString: {0}", hello.ToString());
// Add parameter information to the dynamic method. (This is not
// necessary, but can be useful for debugging.) For each parameter,
// identified by position, supply the parameter attributes and a
// parameter name.
ParameterBuilder parameter1 = hello.DefineParameter(1,ParameterAttributes.In,"message");
ParameterBuilder parameter2 = hello.DefineParameter(2,ParameterAttributes.In,"valueToReturn");
// Display parameter information.
ParameterInfo[] parameters = hello.GetParameters();
Console.WriteLine("\r\nParameters: name, type, ParameterAttributes");
foreach (ParameterInfo p in parameters)
{
Console.WriteLine("\t{0}, {1}, {2}",
p.Name, p.ParameterType, p.Attributes);
}
// Create a delegate that represents the dynamic method.
//This action completes the method, and any further attempts to change the method will cause an exception.
HelloDelegate hi = (HelloDelegate)hello.CreateDelegate(typeof(HelloDelegate));
// Use the delegate to execute the dynamic method.
Console.WriteLine("\r\nUse the delegate to execute the dynamic method:");
int retval = hi("\r\nHello, World!", 42);
Console.WriteLine("Invoking delegate hi(\"Hello, World!\", 42) returned: " + retval);
// Execute it again, with different arguments.
retval = hi("\r\nHi, Mom!", 5280);
Console.WriteLine("Invoking delegate hi(\"Hi, Mom!\", 5280) returned: " + retval);
Console.WriteLine("\r\nUse the Invoke method to execute the dynamic method:");
// Create an array of arguments to use with the Invoke method.
object[] invokeArgs = { "\r\nHello, World!", 42 };
// Invoke the dynamic method using the arguments. This is much
// slower than using the delegate, because you must create an
// array to contain the arguments, and value-type arguments
// must be boxed.
object objRet = hello.Invoke(null, BindingFlags.ExactBinding, null, invokeArgs, new System.Globalization.CultureInfo("en-us"));
Console.WriteLine("hello.Invoke returned: " + objRet);
}
