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VJs Tip Of The Day
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From:
![]() ![]() VishalRJoshi
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Callback functions
Callback functions are powerful tools and we should know how to use them...
In general a callback function is a reference to a method that you pass to
another method... When the second method calls the referenced method , it
actually calls back to the first method... This might be a confusing
terminology but a code snippet from MSDN will probably help make it
clearer...
using System;
using System.Runtime.InteropServices;
public delegate bool CallBack(int hwnd, int lParam);
public class EnumReportApp {
[DllImport("user32")]
public static extern int EnumWindows(CallBack x, int y);
public static void Main()
{
CallBack myCallBack = new CallBack(EnumReportApp.Report);
EnumWindows(myCallBack, 0);
}
public static bool Report(int hwnd, int lParam) {
Console.Write("Window handle is ");
Console.WriteLine(hwnd);
return true;
}
}
Here is the link for you to explore more....
http://msdn.microsoft.com/library/default.asp?url="">l/cpconusingcallbackfunctions.asp
PS: I have coined a new term called "Developer's Superstition"... I suffer
from this problem often - When code does not seem to behave the way I want
it to, knowingly/unknowingly I try things which I know will not work, which
I know are technically impossible but still I do just to make myself feel
good that I have left no stones unturned... I wonder whether you guys also
do such thing... A classic example would be trying to call GC.Collect()
method when a StreamReader is not releazing a file even after calling
close()...{usually its some other process holding the reference...:-)} I
wonder has MS Technologies made me superstitious or is this same
everywhere... :-)
Vishal Joshi
Microsoft MVP .Net
If You Think YOU CAN... You Can...
http://VishalJoshi.Blogspot.com
http://www.microsoft.com/india/mvp/indiamvp.aspx
http://groups.msncom/ChennaiNetUserGroup
http://groups.msn.com/CNUG-DAM
http://groups.msn.com/NetBloomingtonUserGroup
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