public class SerUtils
{
  public static string SerializeToString<T>(T source)
  {
    if(null == source)
	    return string.Empty;
 
    XmlSerializer ser = new XmlSerializer(source.GetType());
    MemoryStream ms = new MemoryStream();
    ser.Serialize(ms, source);			
    ms.Flush();
    ms.Position = 0;
    StreamReader sr = new StreamReader(ms);
    string s = sr.ReadToEnd();
    return s;
  }
 
  public static T DeserializeFromString<T>(string xml)
  {
    if(string.Empty == xml)
	    return default(T);
 
    XmlSerializer ser = new XmlSerializer(typeof(T));
    MemoryStream ms = new MemoryStream();
    StreamWriter sw = new StreamWriter(ms);
    sw.Write(xml);
    sw.Flush();
    ms.Position = 0;
    return (T) ser.Deserialize(ms);
  }
}
 

Don't use this in production!

 
        private static Type GetUnderlyingType<T>(T t)
        {
            return typeof(T);
        }
 

The code above uses Generics and typeof operator to obtain the underlying NullableType. The trick here is to call typeof on the type itself and not the variable. This is not usually possible when you just have a variable but the power of Generics allows you to do so. So, say if you have declared a variable of NullableType int

int? i;

the code in GetUnderlyingType method above does the equivalent of

typeof(int?)

to return the underlying NullableType. To further understand the difference between calling GetType on a variable and using typeof operator on the Type itself, look at the following code.

 
	private static void PrintType<T>(T t)
        {
            Console.WriteLine("{0}, {1}", t.GetType().FullName, typeof(T).FullName);
        }
 

Calling GetType on variable t returns the underlying type where as using typeof operator on Generic type parameter T returns the declared type of variable t.
Given a variable we can further test if the variable holds a NullableType by using the following code.

 
        private static bool IsNullable<T>(T t)
        {
            Type tx = GetUnderlyingType(t);
            return tx.IsGenericType && tx.GetGenericTypeDefinition() == typeof(Nullable<>);
        }
 

The code above obtains the underlying type first and then tests if the type is Generic, and if it is Generic type then it tests for NullableType.

 
int CheckCLRHeader(PBYTE pbFile)
{
    PIMAGE_DOS_HEADER pDOSHeader;
    PIMAGE_NT_HEADERS pNTHeader;
    PIMAGE_OPTIONAL_HEADER32 pNTHeader32;
    PIMAGE_OPTIONAL_HEADER64 pNTHeader64;
    PIMAGE_DATA_DIRECTORY pDataDirectory;
 
	if(NULL == pbFile)
	{
		cout << "Invalid file" << endl;
		return 0;
	}
 
	pDOSHeader = reinterpret_cast
< PIMAGE_DOS_HEADER >(pbFile);
	if(IMAGE_DOS_SIGNATURE != pDOSHeader->e_magic)
	{
		cout << "Cannot find DOS header. Not an executable file" << endl;
		return 0;
	}
 
	pNTHeader = ImageNtHeader(pbFile);
	if(NULL == pNTHeader)
	{
		cout << "Cannot find PE header. Invalid or corrupt file" << endl;
		return 0;
	}
 
	if(IMAGE_NT_SIGNATURE != pNTHeader->Signature)
	{
		cout << "Cannot fine PE signature. Invalid or corrupt file" << endl;
		return 0;
	}
 
	switch(pNTHeader->OptionalHeader.Magic)
	{
		case IMAGE_NT_OPTIONAL_HDR32_MAGIC:
			pNTHeader32 = reinterpret_cast
< PIMAGE_OPTIONAL_HEADER32 >(&pNTHeader->OptionalHeader);
			if(pNTHeader32->NumberOfRvaAndSizes <= IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR)
			{
				cout << "No CLR Data Dictionary. Not a Managed Assembly" << endl;
				return 0;
			}
			pDataDirectory = pNTHeader32->DataDirectory;
			break;
 
		case IMAGE_NT_OPTIONAL_HDR64_MAGIC:
			pNTHeader64 = reinterpret_cast
< PIMAGE_OPTIONAL_HEADER64 >(&pNTHeader->OptionalHeader);
			if(pNTHeader64->NumberOfRvaAndSizes <= IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR)
			{
				cout << "No CLR Data Dictionary. Not a Managed Assembly" << endl;
				return 0;
			}
			pDataDirectory = pNTHeader64->DataDirectory;
			break;
 
		default:
			cout << "Invalid NT header. Invalid or corrupt file" << endl;
			return 0;
	}
 
	if(NULL == pDataDirectory)
	{
		cout << "Cannot find data directories. Invalid or corrupt file" << endl;
		return 0;
	}
 
	if(0 == pDataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].VirtualAddress ||
		0 == pDataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].Size)
	{
		cout << "COM Data Directory not found. Not a Managed Assembly" << endl;
		return 0;
	}
 
	cout << "Managed Assembly" << endl;
 
	return 1;
}
 

The code for check_managed_app function in crtexe.c is similar but slightly different in how it checks for the same IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR but only checks for presence of VirtualAddress.

 
/***
*check_managed_app() - Check for a managed executable
*
*Purpose:
*       Determine if the EXE the startup code is linked into is a managed app
*       by looking for the COM Runtime Descriptor in the Image Data Directory
*       of the PE or PE+ header.
*
*Entry:
*       None
*
*Exit:
*       1 if managed app, 0 if not.
*
*Exceptions:
*
*******************************************************************************/
 
static int __cdecl check_managed_app (
        void
        )
{
        PIMAGE_DOS_HEADER pDOSHeader;
        PIMAGE_NT_HEADERS pPEHeader;
        PIMAGE_OPTIONAL_HEADER32 pNTHeader32;
        PIMAGE_OPTIONAL_HEADER64 pNTHeader64;
 
        pDOSHeader = (PIMAGE_DOS_HEADER)&__ImageBase;
        if ( pDOSHeader->e_magic != IMAGE_DOS_SIGNATURE )
            return 0;
 
        pPEHeader = (PIMAGE_NT_HEADERS)((char *)pDOSHeader +
                                        pDOSHeader->e_lfanew);
        if ( pPEHeader->Signature != IMAGE_NT_SIGNATURE )
            return 0;
 
        pNTHeader32 = (PIMAGE_OPTIONAL_HEADER32)&pPEHeader->OptionalHeader;
        switch ( pNTHeader32->Magic ) {
        case IMAGE_NT_OPTIONAL_HDR32_MAGIC:
            /* PE header */
            /* prefast assumes we are overflowing __ImageBase */
#pragma warning(push)
#pragma warning(disable:26000)
            if ( pNTHeader32->NumberOfRvaAndSizes <=
                    IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR )
                return 0;
#pragma warning(pop)
            return !! pNTHeader32 ->
                      DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR] .
                      VirtualAddress;
        case IMAGE_NT_OPTIONAL_HDR64_MAGIC:
            /* PE+ header */
            pNTHeader64 = (PIMAGE_OPTIONAL_HEADER64)pNTHeader32;
            if ( pNTHeader64->NumberOfRvaAndSizes <=
                    IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR )
                return 0;
            return !! pNTHeader64 ->
                      DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR] .
                      VirtualAddress;
        }
 
        /* Not PE or PE+, so not managed */
        return 0;
}
 

I came across this code while debugging past the main() function. I thought this might be a new piece of code in CRT source that comes with VS2008 only to be proven wrong when searching through the CRT source that comes with all versions of Visual Studio starting from VS2002. Another interesting discovery (at least for me) is that similar code is in various CRT source files. In VS2008 CRT source the files crt0dat.c, crt0.c and crtexe.c contain check_managed_app function in Win32 CRT and crt0dat.c in WinCE CRT. In VS2005 the same function is in crt0.c, crt0dat.c and crtexe.c. In VS2003 and VS2002 it is in crt0.c and crtexe.c. There are other gems of code in CRT source waiting to be discovered!

 
using System;
using System.Diagnostics;
using System.Reflection;
using System.Text;
 
[assembly: DebuggerTypeProxy(typeof(MulticastDelegateDebuggerProxy),
		Target = typeof(MulticastDelegate))]
 
public class MulticastDelegateDebuggerProxy
{
	private string[] m_methods;
 
	public MulticastDelegateDebuggerProxy(System.MulticastDelegate del)
	{
		m_methods = GetMethodList(del);
	}
 
	[DebuggerDisplay(@"Subscribers:\{{Methods.Length}}")]
	public string[] Methods
	{
		get { return m_methods; }
	}
	private string[] GetMethodList(System.MulticastDelegate myEvent)
	{
		string retType = myEvent.Method.ReturnType.Name;
 
		Delegate[] delegates = myEvent.GetInvocationList();
		string[] methods = new string[delegates.Length];
 
		for (int i = 0; i < delegates.Length; ++i)
		{
			Delegate del = delegates[i];
			MethodInfo m = del.Method;
			string accessModifier =
				m.IsPrivate ? "private" : (m.IsPublic ? "public" : (m.IsFamily ? "protected" : ""));
			StringBuilder sb = new StringBuilder();
			foreach (ParameterInfo param in m.GetParameters())
			{
				sb.Append(param.ParameterType.FullName).Append(" ").Append(param.Name).Append(",");
			}
			if (sb.Length > 0)
			{
				sb.Remove(sb.Length - 1, 1);
			}
			string isStatic = m.IsStatic ? "static" : string.Empty;
			string isVirtual = m.IsVirtual ?
				(((m.Attributes & MethodAttributes.NewSlot) == MethodAttributes.ReuseSlot)
				? "override" : "virtual") : string.Empty;
			methods[i] = string.Format("{0} {1} {2} {3} {4}.{5}({6})",
				accessModifier, isStatic, isVirtual, retType, m.ReflectedType.FullName, m.Name, sb.ToString());
		}
 
		return methods;
	}
}

The information displayed in VS2005 by default is shown below.

The information displayed in VS2005 with MulticastDelegateDebuggerProxy is shown below. The MulticastDelegateDebuggerProxy displays fully qualified method name and the parameter names used in the method.

In VS2008, the default information displayed is slightly better than VS2005 as it shows _invocationList by default which can be drilled down to the actual methods. However, the default display can get ambiguous as shown in the screenshot below. The MulticastDelegateDebuggerProxy does a much better job at displaying the same information.

Image courtesy: Dr. Vivek Tailor who is also published in the book.

The JNI specification mentions the naming convention for the native function. However, there is no mention of the fact that when calling the functions from a native library the runtime will try to call the functions using both the decorated and undecorated names. Another peculiar behavior that I noticed is that when calling the other JNI related functions that you can export from a native library such as JNI_OnLoad, JNI_OnUnload, the runtime tries only one decorated name before calling the undecorated function as shown above. I find this very strange.

DEP stands for Data Execution Prevention. It is a hardware based feature supported by Intel as well as AMD processors that disables execution of code that resides in memory areas marked as data pages. On AMD processors, this feature is implemented as NX (No eXecute) bit, and on Intel processors it is implemented as XD (eXecute Disable) bit. An OS can expose this feature and enable the application to take advantage of this protection. Once enabled, it becomes very difficult to inject and run malicious code using popular exploits such as buffer overflow which injects code on stack or heap memory and branches the instruction pointer (EIP) to execute the code. Microsoft has made this feature available in its operating systems starting with the Windows XP Service Pack 2. This feature can be enabled either system wide, or per application in Windows XP Service Pack 2, Windows XP Tablet PC Edition 2005, and Windows Server 2003. In Windows Vista this feature is enabled by default for all the system applications. Vista also has an Opt-out feature that allows you to enable DEP for all the (system as well as user) applications except those on the opt-out list. Robert Hensing explains this is great detail in his post. For VC++ developers there is one more way to take advantage of DEP. Visual Studio 2003 and above provide a linker switch called /NXCOMPAT. This switch sets a bit in the executable that indicates the OS loader that the application is DEP enabled. However, there is one catch. Setting this bit in the executable overrides all the other DEP settings - meaning even if DEP is disabled system wide or the application is opted out of DEP, the OS will still enable DEP for that application!!! This is where the problem starts for applications compiled using .NET 2.0 SP1. The C# compiler was updated to set this bit in the assemblies that it creates, and there is no way to unset it as in VC++ linker. If your application does not use native code, then you have nothing to worry about. If your application uses native then you may be in for a rude shock; your application might suddenly crash with IP_ON_HEAP errors. The old ATL framework generated code on the fly that ran on the stack or heap. If your .NET application uses a component or an ActiveX control that was built using the old ATL framework then your application will fail. The option is to recompile your native code using VS2003 or above. If this is a third party component that the vendor has not updated then you may be out of luck. Don't panic however! There is a ray of hope. You can disable the NXCOMPAT bit set by the C# compiler in the executable using the EditBin utility that is a part of Visual Studio installation. If your assembly is strongly named then you will have to resign it using SN utility. I strongly believe that Microsoft made a horrible mistake by deciding to set this bit by default on all the assemblies. It would have been much better if they had provided a switch just like the C++ linker. This new C# compiler feature is not well publicized by Microsoft. All the .NET developers that I have spoken to so far do not even know what DEP or NXCOMPAT is. Following the pure managed code mantra, most .NET developers do not care about native code any more even if they are using native code in their application. There is still lot of native code out there in the enterprises that is incompatible with DEP. There are lot of .NET applications that use such native code. This creates quite a problem when unknowing developers are faced with a situation when their application(s) suddenly stops working by just recompiling it in .NET 2.0 SP1. There are also other breaking changes as well as new properties, methods and Types added in SP1 as mentioned in a post by Scott Hanselman. This situation is made even worse by the release of Visual Studio 2008 as it installs .NET FX 2.0 SP1. Developers are keen to take advantage of the new features in C# 3.0 in .NET 2.0 applications using VS2008's multi-targeting feature. In an enterprise application development scenario, it is quite possible that developers will have .NET 2.0 SP1 on their development and test machines due to VS2008, but the user desktops will not have SP1. If the application uses new methods or types then it will fail on user desktops. Although one might be inclined to blame developers for developing and testing on environment that differs from the user's environment, such a scenario is highly likely to occur since the changes in .NET 2.0 SP1 are not well known. I have been able to find a list of bug fixes in SP1, but there is no knowledge base article that lists the differences between .NET 2.0 and SP1 other than the few scattered blog entries. It is a very bad idea to make such significant changes in a service pack level release. This is however a reality. . . so developers beware!