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[C#] how bad is it – String Concatenation
+= is often mentioned bad to use in a loop. But how bad is it?
consider the following code:
Stopwatch watch1 = new Stopwatch();
Stopwatch watch2 = new Stopwatch();
String s1 = "";
String s2 = "";
int count = 20000;
watch1.Start();
for (int i = 0; i < count; i++)
{
s1 += i.ToString();
}
watch1.Stop();
Console.WriteLine(watch1.ElapsedMilliseconds);
watch2.Start();
StringBuilder sb = new StringBuilder(s2);
for (int i = 0; i < count; i++)
{
sb.Append(i.ToString());
}
s2 = sb.ToString();
watch2.Stop();
Console.WriteLine(watch2.ElapsedMilliseconds);
Result:
watch1: 2206
watch2: 7
wow…it seems really bad…
[javascript] How bad is it – Modification DOM Tree
a simple test on modification Dom Tree
timing by time.js
Code:
window.onload = function() {
time.start('page load');
var div = document.getElementById("thediv");
var i=5000; while(i--){
div.appendChild(document.createElement("a"));
}
time.stop('page load');
time.start('page load 2');
var div2 = document.getElementById("thediv2");
var fragment = document.createDocumentFragment();
var i=5000; while(i--){
fragment.appendChild(document.createElement("a"));
}
div2.appendChild(fragment.cloneNode(true));
time.stop('page load 2');
time.report();
}
Result: Windows 7 Professional
Firefox 3.6.12
page load: 746ms
page load 2: 371ms
Opera 10.63
page load: 19ms
page load 2: 19ms
IE 8.0.7600.16385
page load: 160ms
page load 2: 152ms
IE 6.0
page load: 140ms
page load 2: 150ms
[Visual Studio] Generat MD5 Checksum After Build
Download:
- MD5sums for Windows
- Unzip it and place it to any folder you want
Configure Post-build event command line:
YOUR_MD5SUMS_PATH “$(TargetPath)”
e.g.
c:\tool\md5sums-1.2\md5sums.exe "$(TargetPath)"
Output
CtpGglMap.dll f81e28e975317a8499af08a9b740be63
[YUI] Things You Should Know About YUI – Throws Error
YAHOO.util.Event.throwErrors is important and often ignored in YUI. The default value for this is false. As a result, any javascript error will be caught and ignored(but written in YUI debug console) in event callback.
e.g.
consider following code:
var evnt = new YAHOO.util.CustomEvent("myevent",{name:"scope"});
evnt.subscribe(
function(type, args, me){
console.log(this);
console.log(args);
console.log(me);
},
{name:"me"})
evnt.fire({name:"args"});
it works fine and print out values in FireBug console. what happen if we make typo
var evnt = new YAHOO.util.CustomEvent("myevent",{name:"scope"});
evnt.subscribe(
function(type, args, me){
console.log(this);
console.lg(args); //typo
console.log(me);
},
{name:"me"})
evnt.fire({name:"args"});
ops….nothing happens. no error message! if one doesn’t spot the typo at first, going to take long time to debug.
the trick is simple and easy
YAHOO.util.Event.throwErrors = true;
[C#] indexer – very interesting feature
indexer , a very very interesting feature in C# to use object as array.
sampe code – FakeDB.cs
usage:
FakeDB db = FakeDB.GetFakeDB();
DataTable table = new DataTable("project");
/* use table */
db["project"] = table;
public class FakeDB
{
//Global Variable
private static FakeDB theFakeDB = null;
//Singleton pattern
private FakeDB() {
Tables = new Dictionary<string, DataTable>();
}
//indexer
public DataTable this[String tname]
{
get
{
if (this.Tables != null && this.Tables.Keys.Contains(tname))
return Tables[tname];
return null;
}
set
{
if (this.Tables != null)
Tables[tname] = value;
}
}
public static FakeDB GetFakeDB()
{
if (theFakeDB == null)
theFakeDB = new FakeDB();
return theFakeDB;
}
public Dictionary<String, DataTable> Tables;
public DataTable GetTable(string name)
{
if (Tables.Keys.Contains(name))
return Tables[name];
else
return null;
}
public void SetTable(String name, DataTable table)
{
Tables[name] = table;
}
}
[javascript] console.log in IE
console.log has been a wonderful functionality in firebug/firefox. Sadly, there is no such feature in IE(i personally don’t like debugger). A simple logger for IE is implemented to make console.log works under IE
Snapshot:
How to use:
include:
<link href="css/ctp.log.css" rel="stylesheet" type="text/css"/> <!-- JSON.stringify is used for stringify object. Remove if don't need --> <script language = "javascript" src="js/json2.js"></script> <script language = "javascript" src="js/ctp.log.js">
use:
//use it as console.log in Firefox
<script>
for(var x =0; x<10; x++){
//logging before UI is rendered
console.log({"value":x, "time":new Date()});
}
</script>
Download:
from Sourceforge
[C++/CLI] How to throw a .NET exception
Recently cooperate with a Taiwan university lab. They use C++ to code a core library for our .NET developers to use. Here is how to throw a .NET exception in C++/CLI
public:
int divide(int a, int b)
{
if(b==0)
throw gcnew System::Exception("It is a C++\CLI exception, can not divided by zero");
}
[javascript]goto link later
here is the javascript code for preventing redirect when user clicks on a html anchor
javascript:
var url = {};
function addEvent(el, type, evt){
if(el){
if ( document.addEventListener ) {
el.addEventListener( type, evt, false );
} else if ( document.attachEvent ) {
type="on"+type;
el.attachEvent( type, evt );}}
}
function log4link0(el){
addEvent(el, "click", function(evt){
var lv = el.getAttribute("href");
if(lv){
/* record the clicked href */
console.log("going to:"+lv);
url.value = lv;}
/* stop click event */
if(evt){
if (evt.stopPropagation ){
evt.stopPropagation();
evt.preventDefault();
}else{
window.event.cancelBubble = true;
window.event.returnValue = false;}
}
});
}
function log4link(){
var lks = document.getElementsByTagName("a");
if(lks){
var i=lks.length; while(i--){
log4link0(lks[i]);}}
/* register click event to element*/
addEvent(document.getElementById("goto"), "click", function(){
if(url && url.value)
window.location = url.value;
});
}
/* registr event on document load */
if ( document.addEventListener ) {
document.addEventListener( "DOMContentLoaded", log4link, false );
} else if ( document ) {
document.attachEvent("onreadystatechange",function(){
if ( document.readyState === "complete" ) {log4link();}
});}
html:
<body> <a href="http://www.google.com">Google</a> <a href="http://www.yahoo.com">YAHOO!</a> <a href="http://www.baidu.com">Baidu</a> <a id="goto">continue</a> </body>
i also “componentlized” this into a light-weight and independent javascript js library, called Go2Later
[C#] about Clone
fooObj obj1 = new fooObj() { Name = "Aval" };
fooObj obj2 = (fooObj)obj1.Clone();
fooObj obj3 = (fooObj)obj1.CloneWithSerialization();
fooObj obj4 = obj1;
fooObj obj5 = (fooObj)obj1.ShallowCopy();
System.Diagnostics.Debug.WriteLine(obj1 == obj2);
System.Diagnostics.Debug.WriteLine(obj1 == obj3);
System.Diagnostics.Debug.WriteLine(obj1 == obj4);
System.Diagnostics.Debug.WriteLine(obj1 == obj5);
System.Diagnostics.Debug.WriteLine(obj1.Equals(obj2));
System.Diagnostics.Debug.WriteLine(obj1.Equals(obj3));
System.Diagnostics.Debug.WriteLine(obj1.Equals(obj4));
System.Diagnostics.Debug.WriteLine(obj1.Equals(obj5));
[Serializable]
class fooObj: ICloneable, ISerializable
{
public String Name { get; set; }
public override bool Equals(object obj)
{
if (obj == this)
return true;
else if (obj == null)
return false;
else
return (obj.GetType() == typeof(fooObj) && this.Name.Equals(((fooObj)obj).Name));
}
public override int GetHashCode()
{
return base.GetHashCode();
}
public object Clone()
{
return new fooObj() { Name = this.Name };
}
public object MemberwiseClone()
{
return this.MemberwiseClone();
}
public object CloneWithAs()
{
return (new fooObj(){Name=this.Name}) as object;
}
public object ShallowCopy()
{
return this;
}
public object CloneWithSerialization()
{
using (Stream objects = new MemoryStream())
{
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(objects, this);
objects.Seek(0, SeekOrigin.Begin);
return formatter.Deserialize(objects);
}
}
public fooObj() { }
#region ISerializable Members
[SecurityPermissionAttribute(SecurityAction.Demand,
SerializationFormatter = true)]
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.AddValue("Name", this.Name);
}
protected fooObj(SerializationInfo info, StreamingContext context)
{
this.Name = info.GetString("Name");
}
#endregion
}
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