Examining the method body using Reflection in .NET C#
October 7, 2014 1 Comment
In this short post we saw how to extract the members of a class: constructors, properties, methods etc. Even more exciting is the fact that you can peek into the body of a method. Well, not the plain text C# or VB code, but the Intermediate Language – MSIL version of it.
The MethodBody object represents, as the name suggests, the body of a method including the local variables and the MSIL instructions. MethodBody is available on classes that derive from the MethodBase class, which are methods and constructors – MethodInfo and ConstructorInfo.
Consider the following Customer class:
public class Customer { private string _name; public Customer(string name) { if (string.IsNullOrEmpty(name)) throw new ArgumentNullException("Customer name!"); _name = name; } public string Name { get { return _name; } } public string Address { get; set; } public int SomeValue { get; set; } public int ImportantCalculation() { int variable = 2; string stringVar = string.Empty; if (variable == 2) { stringVar = "two"; } else { stringVar = "hello"; } ImportantVoidMethod(); return 1000; } public void ImportantVoidMethod() { bool ok = false; SomeEnumeration enumeration = SomeEnumeration.ValueOne; switch (enumeration) { case SomeEnumeration.ValueOne: ok = true; break; case SomeEnumeration.ValueTwo: ok = false; break; default: ok = false; break; } } public enum SomeEnumeration { ValueOne = 1 , ValueTwo = 2 } public class SomeNestedClass { private string _someString; } }
The following code shows you how you can extract the methods and inspect them:
Type customerType = typeof(Customer); Console.WriteLine("Customer methods: "); MethodInfo[] methods = customerType.GetMethods(); foreach (MethodInfo mi in methods) { Console.WriteLine(mi.Name); MethodBody methodBody = mi.GetMethodBody(); if (methodBody != null) { byte[] ilCode = methodBody.GetILAsByteArray(); int maxStackSize = methodBody.MaxStackSize; IList<LocalVariableInfo> localVariables = methodBody.LocalVariables; Console.WriteLine("Max stack size: {0}", maxStackSize); Console.WriteLine("Local variables if any:"); foreach (LocalVariableInfo lvi in localVariables) { Console.WriteLine("Type: {0}, index: {1}.", lvi.LocalType, lvi.LocalIndex); } Console.WriteLine("IL code:"); StringBuilder stringifiedIlCode = new StringBuilder(); foreach (byte b in ilCode) { stringifiedIlCode.Append(string.Format("{0:x2} ", b)); } Console.WriteLine(stringifiedIlCode); } }
The MethodInfo array will include the properties that are turned into methods, e.g. Name will become get_Name, and also the methods inherited from Object such as ToString(). Here’s the output for ImportantVoidMethod and ImportantCalculation:
The LocalVariableInfo doesn’t contain the name of the variable because the metadata about a type doesn’t keep the variable name, only its order.
View all posts on Reflection here.
so………. how do you get the value? the name you can get it from the MethodInfo.GetParameters.
Without the values, sadly, this is not useful