Monthly Archives: March 2009

Lambda based reflection Vs Normal reflection Vs Direct call

25 March 2009
Comments (2)

One friend of mine sent me the following code sample that really surprised me.

There are three different approaches being used to call a method from a different class. The approaches are -

  1. Direct Call
  2. Call through Lambda based reflection
  3. Call through Normal Reflection

It was really surprising to see the execution speed comparison between three different approaches. The lambda based approach was found to be the fastest by the order of 1000 times.

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Reflection;
 
namespace LambdaReflection
{
 
    class MyClass
    {
        public void CallIt()
        {
        }
    }
 
    class Program
    {
        delegate void LocalDel<t>(T mc);
        static void Main(string[] args)
        {
            System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
            MethodInfo minfo = typeof(MyClass).GetMethod("CallIt", BindingFlags.Instance | BindingFlags.Public);
            MyClass obj = new MyClass();
 
            //compile expression tree
            LocalDel<myclass> lambdaExpression = FuncCallIt<myclass>("CallIt");
            sw.Reset();
            sw.Start();
 
            //Direct call by using object
            for (int a = 0; a &lt; 10000; a++)
            {
                obj.CallIt();
            }
            sw.Stop();
            Console.WriteLine(string.Format("Time taken by Direct call {0}", sw.ElapsedTicks));
            sw.Reset();
            sw.Start();
 
            //dynamically compiled lambda call
            for (int a = 0; a &lt; 10000; a++)
            {
                lambdaExpression(obj);
            }
            sw.Stop();
            Console.WriteLine(string.Format("Time taken by lambda-expression compilation {0}", sw.ElapsedTicks));
            sw.Reset();
            sw.Start();
 
            //reflection call
            for (int a = 0; a &lt; 10000; a++)
            {
                minfo.Invoke(obj, null);
            }
            sw.Stop();
            Console.WriteLine(string.Format("Time taken by Reflection call {0}", sw.ElapsedTicks));
            Console.ReadLine();
 
        }
        private static LocalDel<t> FuncCallIt<t>(string MethodName)
        {
            var target = Expression.Parameter(typeof(T), "a");
            MethodInfo minfo = typeof(T).GetMethod(MethodName, BindingFlags.Instance | BindingFlags.Public);
            var methodinvokeExpression = Expression.Call(target, minfo);
            var lambda = Expression.Lambda<localdel><t>&gt;(methodinvokeExpression, new ParameterExpression[] { target });
            return lambda.Compile();
        }
    }
}

Following is the result of the execution on my system:

Time taken by Direct call 2384625

Time taken by lambda-expression compilation 902430

Time taken by Reflection call 518534265

I didn’t expect lambda based call to be faster than direct call but I need to explore as how best I can make use of this knowledge in my real programming scenarios. The compiled lambda demands different compiled lambda expressions for each method being used. However, if performance is the prime objective in the application then I think this tangential approach is worth considering.

What is your opinion on it ?

Mark File for deletion on reboot

24 March 2009
Comments (0)

Requirement: Delete files from a given folder using C#.

Challenge: The file may be in use i.e. locked.

Approach: Use System Call to mark file for deletion on restart

Solution: Use PInvoke for MoveFileEx.

///
/// Consts defined in WINBASE.H
///
internal enum MoveFileFlags
{
    MOVEFILE_REPLACE_EXISTING = 1,
    MOVEFILE_COPY_ALLOWED = 2,
    MOVEFILE_DELAY_UNTIL_REBOOT = 4,
    MOVEFILE_WRITE_THROUGH  = 8
}
 
 
/// <summary>
/// Marks the file for deletion during next system reboot
/// </summary>
/// <param name="lpExistingFileName">The current name of the file or directory on the local computer.</param>
/// <param name="lpNewFileName">The new name of the file or directory on the local computer.</param>
/// <param name="dwFlags">MoveFileFlags</param>
/// <returns>bool</returns>
/// <remarks>http://msdn.microsoft.com/en-us/library/aa365240(VS.85).aspx</remarks>
[System.Runtime.InteropServices.DllImportAttribute("kernel32.dll",EntryPoint="MoveFileEx")]
internal static extern bool MoveFileEx(string lpExistingFileName, string lpNewFileName,
MoveFileFlags dwFlags);
 
//Usage for marking the file to delete on reboot
MoveFileEx(fileToDelete, null, MoveFileFlags.MOVEFILE_DELAY_UNTIL_REBOOT);

The file is marked for deletion in registry in following location

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerPendingFileRenameOperations

Uninstallation from C#

17 March 2009
Comments (0)

I wanted to programatically uninstall an application installed in my system. Following code is a working piece to uninstall any custom application from the system.

Note: Following code snippet is not the best example of good coding standards ! It was just a sample I was trying to use to achieve something. The code is a mixture of coding styles lifted across various sites. Please excuse for that :) 

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private static int Uninstall()
{
        Microsoft.Win32.RegistryKey Fregistry =
        Microsoft.Win32.Registry.LocalMachine.OpenSubKey("SOFTWARE")
        .OpenSubKey("Microsoft").OpenSubKey("Windows").OpenSubKey("CurrentVersion")
        .OpenSubKey("Installer").OpenSubKey("UserData")
        .OpenSubKey("S-1-5-18").OpenSubKey("Products");
        string[] Names = Fregistry.GetSubKeyNames();
        string uninstall = "";
        string ApplicationName = "My Custom Application";
        for (int i = 0; i < Names.Length; i++)
        {
            Microsoft.Win32.RegistryKey FTemp = Fregistry.OpenSubKey(Names[i]).OpenSubKey("InstallProperties");
            if (FTemp == null)
                continue;
            string appFound = (FTemp.GetValue("DisplayName") == null) ? String.Empty : FTemp.GetValue("DisplayName").ToString();
            if (!String.IsNullOrEmpty(appFound))
                System.Diagnostics.Trace.WriteLine("Found Software: " + appFound);
            if (String.Compare(appFound, ApplicationName, true) == 0)
            {
                String installedVersion = FTemp.GetValue("DisplayVersion").ToString();
                if (!installedVersion.StartsWith("3.1."))//can be removed if only one version is installed
                    continue;
                object obj = FTemp.GetValue("UninstallString");
                if (obj == null)
                    uninstall = "";
                else
                    uninstall = obj.ToString();
                i = Names.Length;
            }
        }
        if (String.IsNullOrEmpty(uninstall))
        {
            return -1;
        }
        System.Console.WriteLine(uninstall);
        System.Diagnostics.Process FProcess = new System.Diagnostics.Process();
        string temp = "/passive /x{" + uninstall.Split("/".ToCharArray())[1].Split("I{".ToCharArray())[2];
        FProcess.StartInfo.FileName = uninstall.Split("/".ToCharArray())[0];
        FProcess.StartInfo.Arguments = temp;
        FProcess.StartInfo.UseShellExecute = false;
        FProcess.Start();
        FProcess.WaitForExit();
        if (FProcess.ExitCode != 0)
            return -1;
        else
        {
            return 0;
        }
}