Experimenting with Dynamic Code Generation

Simplified experiment using Reflection.Emit to dynamically generate functions.

How it Works

Rather than dynamically invoking a method via Reflection, a simplified wrapper function is generated + created.

Examples

Simply compile + invoke. Previous compilations for a MethodInfo are cached internally.

Static Members

public static class TestClass
{
    public static void MethodWithArgsAndNoReturn(int a, int b)
    {
        Console.WriteLine($"Output is {a + b}");
    }
}


var owningType = typeof(TestClass);
var methodInfo = owningType.GetMethod(nameof(TestClass.MethodWithArgsAndNoReturn));
var compiledMethod = methodInfo.Compile();
methodHasArgsNoReturn.Invoke(2, 5);

Return Types

For members with return types, they can be provided using the generic version of Compile<T>():

public static class TestClass
{
    public static int MethodWithArgsAndReturn(int a, int b)
    {
        return a + b;
    }
}


var owningType = typeof(TestClass);
var methodInfo = owningType.GetMethod(nameof(TestClass.MethodWithArgsAndReturn));
var compiledMethod = methodInfo.Compile<int>();
var result = methodHasArgsNoReturn.Invoke(2, 5);

Instance Members

For instance members, the WithInstance<T>(TInstance) function will associate the instance of the class with the non-static method.

public class TestClass
{
    public int MethodWithArgsAndReturn(int a, int b)
    {
        return a * b;
    }
}


var instance = new TestClass();
var methodInfo = instance.GetType().GetMethod(nameof(TestClass.MethodWithArgsAndReturn));
var compiledMethod = methodInfo.Compile<int>();
var result = methodHasArgsNoReturn.WithInstance(instance).Invoke(2, 5);

Properties and Fields

For properties and fields, the same conventions apply. As properties and fields can be both set and get, they must be accessed through Get and Set.

public class TestClass
{
    public int PropertyTest { get; set; }
}

var instance = new TestClass();
var memberInfo = instance.GetType().GetProperty(nameof(TestClass.PropertyTest));

var member = memberInfo.Compile<int>().WithInstance(instance);

member.Set.Invoke(42);
var value = member.Get.Invoke(42);

Alternately, CompileSetter and CompilerGetter methods are also directly available.

public class TestClass
{
    public int PropertyTest { get; set; }
}

var instance = new TestClass();
var memberInfo = instance.GetType().GetProperty(nameof(TestClass.PropertyTest));

var setter = memberInfo.CompileSetter<int>().WithInstance(instance);
var getter = memberInfo.CompileGetter<int>().WithInstance(instance);

setter.Invoke(42);
var value = getter.Invoke(42);

Benchmarks

A few benchmarks as run from my machine.

Method	Mean	Error	StdDev	Median
Codegen_GenerateAndInvoke	134.18 ns	2.7031 ns	6.0459 ns	130.87 ns
Codegen_BareInvoke	27.57 ns	1.2707 ns	3.7467 ns	28.66 ns
Codegen_BareInvoke_WithInstance	37.81 ns	0.6034 ns	0.5644 ns	37.62 ns
Reflection_BareInvoke	250.10 ns	1.5043 ns	1.4071 ns	250.50 ns