I am using a enum
public enum WatchUsageMode
{
Watch = 1,
EmailPreferences = 2
}
i want to set the property of that enum in my view state in such a way that whenever view state is null return Watch else EmailPreference.how can i get and set the property?
Create a property to encapsulate this
public WatchUsageMode WatchUsageModeValue
{
get
{
if(ViewState["WatchUsageModeValue"] != null &&
ViewState["WatchUsageModeValue"] is WatchUsageMode)
return (WatchUsageMode)ViewState["WatchUsageModeValue"];
else
return null;
}
set
{
ViewState["WatchUsageModeValue"] = value;
}
}
Setting:
ViewState["KeyString"] = WatchUsageMode.EmailPreferences
Getting From View State
WatchUsageMode get()
{
if(ViewState["KeyString"]!=null)
return (WatchUsageMode)ViewState["KeyString"];
return WatchUsageMode.Watch;
}
Related
I have a static method in a helper class named helper.getdiscount(). This class is ASP.NET frontend code and used by UI pages.
Inside this method I check if some data is in the ASP.NET cache then return it, otherwise it makes a service call and store the result in the cache and then returns that value.
Will this be a problem considering multiple threads might be accessing it at the same time?
if (HttpContext.Current.Cache["GenRebateDiscountPercentage"] == null)
{
IShoppingService service = ServiceFactory.Instance.GetService<IShoppingService>();
rebateDiscountPercentage= service.GetGenRebateDiscountPercentage().Result;
if (rebateDiscountPercentage > 0)
{
HttpContext.Current.Cache.Add("GenRebateDiscountPercentage", rebateDiscountPercentage, null, DateTime.Now.AddDays(1), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Normal, null);
}
}
else
{
decimal.TryParse(HttpContext.Current.Cache["GenRebateDiscountPercentage"].ToString(), out rebateDiscountPercentage);
}
Please advise if this is fine or any better approach could be used.
try something like this with lock object.
static readonly object objectToBeLocked= new object();
lock( objectToBeLocked)
{
if (HttpContext.Current.Cache["GenRebateDiscountPercentage"] == null)
{
IShoppingService service = ServiceFactory.Instance.GetService<IShoppingService>();
rebateDiscountPercentage= service.GetGenRebateDiscountPercentage().Result;
if (rebateDiscountPercentage > 0)
{
HttpContext.Current.Cache.Add("GenRebateDiscountPercentage", rebateDiscountPercentage, null, DateTime.Now.AddDays(1), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Normal, null);
}
}
else
{
decimal.TryParse(HttpContext.Current.Cache["GenRebateDiscountPercentage"].ToString(), out rebateDiscountPercentage);
}
}
Also you can look into following thread.
What is the best way to lock cache in asp.net?
Use these generic methods to use the cache for any type:
`public static void AddCache(string key, object Data, int minutesToLive = 1440)
{
if (Data == null)
return;
HttpContext.Current.Cache.Insert(key, Data, null, DateTime.Now.AddMinutes(minutesToLive), Cache.NoSlidingExpiration);
}
public static T GetCache<T>(string key)
{
return (T)HttpContext.Current.Cache.Get(key);
} `
Now to solve your problem:
`if(GetCache<decimal>("GenRebateDiscountPercentage") == null)
{
IShoppingService service = ServiceFactory.Instance.GetService<IShoppingService>();
rebateDiscountPercentage= service.GetGenRebateDiscountPercentage().Result;
if (rebateDiscountPercentage > 0)
{
AddCache("GetGenRebateDiscountPercentage", rebateDiscountPercentage);
}
}
else
{
rebateDiscountPercentage = GetCache<decimal>("GetGenRebateDiscountPercentage");
}
`
I have a object that is extended from arraycollection. This object has to access and manipulate the arraycollections source object. When this happens, the local sorted/filter copy of data goes out of sync with the source data. To line things up correctly, the sort/filter needs to be re-applied.
To do this normally, you would call refresh() on the arraycollection, but this also broadcasts a refresh event. What I want is to update the sort/filter without dispatching an event.
Having looked into the ArrayCollection class, I can see it is extended from ListCollectionView. The refresh function
public function refresh():Boolean
{
return internalRefresh(true);
}
is in ListCollectionView and it calls this function
private function internalRefresh(dispatch:Boolean):Boolean
{
if (sort || filterFunction != null)
{
try
{
populateLocalIndex();
}
catch(pending:ItemPendingError)
{
pending.addResponder(new ItemResponder(
function(data:Object, token:Object = null):void
{
internalRefresh(dispatch);
},
function(info:Object, token:Object = null):void
{
//no-op
}));
return false;
}
if (filterFunction != null)
{
var tmp:Array = [];
var len:int = localIndex.length;
for (var i:int = 0; i < len; i++)
{
var item:Object = localIndex[i];
if (filterFunction(item))
{
tmp.push(item);
}
}
localIndex = tmp;
}
if (sort)
{
sort.sort(localIndex);
dispatch = true;
}
}
else if (localIndex)
{
localIndex = null;
}
revision++;
pendingUpdates = null;
if (dispatch)
{
var refreshEvent:CollectionEvent =
new CollectionEvent(CollectionEvent.COLLECTION_CHANGE);
refreshEvent.kind = CollectionEventKind.REFRESH;
dispatchEvent(refreshEvent);
}
return true;
}
annoyingly, that function is private and so is unavailable to and class that extends ListCollectionView. Also, a lot of what is in the internalRefresh function is private too.
Does anyone know of a way to call internalRefresh from a class that extends ArrayCollection? Or a way of stopping the refresh event from being dispatched when refresh is called?
My (read:hack) solution to this:
addEventListener(CollectionEventKind.REFRESH, handlerHack, true);
The true adds this listener onCapture, before anyone else gets to act on the event.
Before you call the collection.refresh() to update sort/filter, set a boolean flag to true.
discardRefreshEvent = true;
myCol.refresh();
In the listener...
private function handlerHack(evt:CollectionEvent):void
{
if (discardRefreshEvent)
{
evt.stopImmediatePropagation();
discardRefreshEvent = false;
}
}
Disclaimer: Haven't done this exact use before (have implemented similar functionality with other events), also only guessing on Event types/names.
maybe you could extend ArrayCollection, listen to the refresh event and call stopImmediatePropagation() on it when it is fired ? I would start with this...
Good luck :-)
If I have a read-only property on an object that fills itself via the DB, is this what I should be doing, or is there a better way to make sure it's already been evaluated?
private List<Variable> _selectedVariables;
public new List<Variable> SelectedVariables
{
get
{
if (_selectedVariables == null)
{
_selectedVariables = SomeFunctionThatCallsDB();
}
return _selectedVariables;
}
}
That's fine for a single thread; but you will have problems if that is going to be in a situation where you have multithreaded gets.
EDIT: Threadsafing:
Simple Threadsafe pattern:
private readonly object _objectLock = new object();
private List<T> _someList = null;
public List<T> MyStuff
{
get
{
if(_someList == null)
{
lock(_objectLock)
{
if(_someList == null)
_someList = LoadFromDB();
}
}
return _someList;
}
}
You check to see if set, then lock, then check again to make sure you covered the race condition.
My goal is to create a generic function that selects a value in a combobox accoring to a value.
(My comoBox holds arrayCollection as dataProvider.)
The difficulty is infact to get a propertyname in runtime mode
public function selectComboByLabel(combo:ComboBox , propetryName:String, value:String):void {
var dp:ArrayCollection = combo.dataProvider as ArrayCollection;
for (var i:int=0;i<dp.length;i++) {
if (dp.getItemAt(i).propertyName==value) {
combo.selectedIndex = i;
return;
}
}
}
the line if (dp.getItemAt(i).propertyName==value)
is of course incorrect.
It should be arther something like: dp.getItemAt(i).getPropertyByName(propertyName)
Any clue on how to that ?
Don't use Object Property notation. Do this:
dp.getItemAt(i)[propertyName]
In addition to what Flextras said, you could also redo your for loop to make it easier to read:
for each(var item:Object in dp) {
if(item[propertyName] == value) {
combo.selectedItem = item;
return;
}
}
I want to check in my function if a passed argument of type object is empty or not. Sometimes it is empty but still not null thus I can not rely on null condition. Is there some property like 'length'/'size' for flex objects which I can use here.
Please help.
Thanks in advance.
If you mean if an Object has no properties:
var isEmpty:Boolean = true;
for (var n in obj) { isEmpty = false; break; }
This is some serious hack but you can use:
Object.prototype.isEmpty = function():Boolean {
for(var i in this)
if(i != "isEmpty")
return false
return true
}
var p = {};
trace(p.isEmpty()); // true
var p2 = {a:1}
trace(p2.isEmpty()); // false
You can also try:
ObjectUtil.getClassInfo(obj).properties.length > 0
The good thing about it is that getClassInfo gives you much more info about the object, eg. you get the names of all the properties in the object, which might come in handy.
If object containes some 'text' but as3 doesn't recognize it as a String, convert it to string and check if it's empty.
var checkObject:String = myObject;
if(checkObject == '')
{
trace('object is empty');
}
Depends on what your object is, or rather what you expect it to have. For example if your object is supposed to contain some property called name that you are looking for, you might do
if(objSomeItem == null || objSomeItem.name == null || objSomeItem.name.length == 0)
{
trace("object is empty");
}
or if your object is actually supposed to be something else, like an array you could do
var arySomeItems = objSomeItem as Array;
if(objSomeItem == null || arySomeItems == null || arySomeItems.length == 0)
{
trace("object is empty");
}
You could also use other ways through reflection, such as ObjectUtil.getClassInfo, then enumerate through the properties to check for set values.... this class help:
import flash.utils.describeType;
import flash.utils.getDefinitionByName;
public class ReflectionUtils
{
/** Returns an Array of All Properties of the supplied object */
public static function GetVariableNames(objItem:Object):Array
{
var xmlPropsList:XMLList = describeType(objItem)..variable;
var aryVariables:Array = new Array();
if (xmlPropsList != null)
{
for (var i:int; i < xmlPropsList.length(); i++)
{
aryVariables.push(xmlPropsList[i].#name);
}
}
return aryVariables;
}
/** Returns the Strongly Typed class of the specified library item */
public static function GetClassByName($sLinkageName:String):Class
{
var tObject:Class = getDefinitionByName($sLinkageName) as Class;
return tObject;
}
/** Constructs an instance of the speicified library item */
public static function ConstructClassByName($sLinkageName:String):Object
{
var tObject:Class = GetClassByName($sLinkageName);
//trace("Found Class: " + tMCDefinition);
var objItem:* = new tObject();
return objItem;
}
public static function DumpObject(sItemName:String, objItem:Object):void
{
trace("*********** Object Dump: " + sItemName + " ***************");
for (var sKey:String in objItem)
{
trace(" " + sKey +": " + objItem[sKey]);
}
}
//}
}
Another thing to note is you can use a simple for loop to check through an objects properties, thats what this dumpobject function is doing.
You can directly check it as follow,
var obj:Object = new Object();
if(obj == null)
{
//Do something
}
I stole this from a similar question relating to JS. It requires FP 11+ or a JSON.as library.
function isEmptyObject(obj){
return JSON.stringify(obj) === '{}';
}
can use use the hasProperty method to check for length
var i:int = myObject.hasProperty("length") ? myObject.length: 0;