|
|
John Simmons / outlaw programmer wrote: using (using (FileStream fs = new FileStream(path, FileMode.Create, FileAccess.ReadWrite, FileShare.None))
I think this statement is wrong. You can use nested using statements in this way
using(DisposableObject1)
using(DisposableObject2)
{
}
John Simmons / outlaw programmer wrote: but doesn't the same thing happen when the object goes out of scope?
Do you mean it will be disposed when the scope ends ? GC will handle it, but there would be a delay in disposal. This will produce same IL which try/finally is producing. So it's just a syntactic shortcut to call Dispose() method which ensures immediate disposal.
|
|
|
|
|
John Simmons / outlaw programmer wrote: but doesn't the same thing happen when the object goes out of scope?
Yes but garbage collection is non-deterministic and using offers deterministic resource clean up. I'm just the messenger, don't shoot me!
led mike
|
|
|
|
|
GC and dispose are also doing different stuff.
GC frees the memory allocated by the managed object.
Dispose is supposed to release native resources allocated by an object.
So even if you call dispose, the managed object is still present untill it gets eaten by the GC.
|
|
|
|
|
John Simmons / outlaw programmer wrote: I realize that this ensures that everything will be properly closed and disposed without you having to do anything, but doesn't the same thing happen when the object goes out of scope?
No, it doesn't. The memory management doesn't use reference counting, which means that nothing happens because of an object going out of scope.
Because there is no possibility to add any code that will run when the object goes out of scope, the IDisposable interface was created, so that the lifetime of an object could be controlled from the code.
Ordinary objects that doesn't have a specific need for any cleanup, doesn't have a Dispose method. They will just be removed when the garbage collector notices that the can be.
Despite everything, the person most likely to be fooling you next is yourself.
|
|
|
|
|
>>so that the lifetime of an object could be controlled from the code.
rather: Lifetime of resources used by an object could be controlled from the code.
The disposable object itself will not be removed from memory when you call dispose on it..
|
|
|
|
|
Roger Alsing wrote: rather: Lifetime of resources used by an object could be controlled from the code.
Good point. I should have said that it's for controlling the life cycle of the object rather than the lifetime.
Despite everything, the person most likely to be fooling you next is yourself.
|
|
|
|
|
John Simmons / outlaw programmer wrote: I realize that this ensures that everything will be properly closed and disposed without you having to do anything, but doesn't the same thing happen when the object goes out of scope?
Not when the object goes out of scope, but when the GC runs and that too only if the object has a finalizer. Garbage collection cleans up the object itself; it doesn't attempt to clean up any resources held by the object. IDisposable (and the finalizer) do the resource cleanup part.
|
|
|
|
|
See http://www.codeproject.com/KB/cs/tinguusingstatement.aspx[^]
John Simmons / outlaw programmer wrote: Is it wrong to not want to sue this construct in favor of more obvious code?
Do you want to type out all the try-finally-dispose things again and again, or understand using once and save the typing (AND reading)?
edit: omfg, it took me 30min to write this and find a link  there wasnt any replies when i started typing...
[ My Blog] "Visual studio desperately needs some performance improvements. It is sometimes almost as slow as eclipse." - Rüdiger Klaehn "Real men use mspaint for writing code and notepad for designing graphics." - Anna-Jayne Metcalfe
|
|
|
|
|
dnh wrote: edit: omfg, it took me 30min to write this and find a link there wasnt any replies when i started typing...
Sorry - I just typed my answer from memory which was why I missed a null check. 
|
|
|
|
|
What's with the extra using ( ?
|
|
|
|
|
Wasn't this the OP's question?
-Spacix
All your skynet questions[ ^] belong to solved
I dislike the black-and-white voting system on questions/answers. 
|
|
|
|
|
|
Does anyone know a simple way to do this?
I suppose I could convert the createTimeStamp object to a string, and then use a terrible method to break the pieces down to individual objects, then pass those objects to another method through interfaces that creates the DateTime object, however that seems awefully redundant and I am sure someone has a much better way of doing it.
Any help is appreciated.
psuedocode sample (of what I would "like" to do):
foreach (SearchResult result in results)
{
int date = Convert.ToDateTime(result.Properties["createTimeStamp"][0]);
DateTime today = DateTime.UtcNow;
TimeSpan diff = today - date;
}
modified on Tuesday, May 6, 2008 10:09 AM
|
|
|
|
|
You know, I have been working on this for hours, and by posting this and then modifying it with the psuedocode, I ended up answering my own question.
int date = ...
should read
DateTime date = ...
Thank to anyone who put any thought into this.
Scot
|
|
|
|
|
I have a series of fairly large enums, and each value within them has a free text equivalent.
Within my code, I need to get the free text for a given enum value. Currently I am using a fairly traditional method of doing this, i.e. a switch/case on the enum value which obtains the text description.
However this is proving to be a pain to maintain, so does anybody know of a way of adding the free text as an attribute of the enum. For example
public enum MyEnum
{
[Description("This Wibbles")]
Value1,
[Description("This Wobbles")]
Value2,
[Description("Ding Dong")]
Value3
}
|
|
|
|
|
See here [^].
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
|
|
|
|
|
The description attribute is exactly what I personally use for this, with a simple helper method to obtain the description from the enum item:
<code>public static class EnumHelper
{
public static string GetDescription(System.Enum enumValue)
{
FieldInfo fi = enumValue.GetType().GetField(enumValue.ToString());
object[] descAttribs = fi.GetCustomAttributes(typeof(DescriptionAttribute), true);
if (descAttribs.Length == 0)
return null;
return ((DescriptionAttribute)descAttribs[0]).Description;
}
}</code>
Usage:
string description = EnumHelper.GetDescription(MyEnum.Value1);
Hope that helps.
|
|
|
|
|
Thanks alot, that works perfectly
Out of curiosity, is it possible to add object type attributes?
for example
public enum EnumAlpha
{
value1,
value2
}
public enum EnumBeta
{
[ObjectDescription(EnumAlpha.value1)]
value1,
[ObjectDescription(EnumAlpha.value2)]
value2,
}
|
|
|
|
|
I dont see what you're trying to achieve, but the answer is yes, you can define your own attributes and markup your code with those attributes.
|
|
|
|
|
Well to cut a very long story short I am currently in the throws of creating an XML data transformation library. Unfortunately for me neither XML structure can be schema'd and these are also out of my control and cannot be change.
To get around this I have created a series of enums for the 100's of different keys these items contain, so now I am trying to create mapping data from one to the other.
It could be done with switch/case statements, however this is messy and will be complicated to maintain. So I am attempting to use attributes on the input enums to easily convert these to the output format.
So for example each data structure contains the concept of Address Type, e.g.
public enum OutputAddressType
{
[Description("ResidentialAddress")]
Residential,
[Description("CommercialAddress")]
Commericial,
[Description("UnknownAddress")]
Unknown,
}
public enum InputAddressType
{
[Description("ADR001")]
Home,
[Description("ADR002")]
HomeSecondary,
[Description("ADR003")]
Business
}
Now as I iterate through the input data object address values, I currently have a switch case that looks something like this:
switch(input.AddressType)
{
case InputAddressType.Home:
this.output.AddressType = OutputAddressType.ResidentialAddress;
break;
case InputAddressType.HomeSecondary:
this.output.AddressType = OutputAddressType.Unknown;
break;
case InputAddressType.Business:
this.output.AddressType = OutputAddressType.CommercialAddress;
break;
}
It would be great if I could do something like this to the input enum:
public enum InputAddressType
{
[ObjectDescription(InputAddressType.ResidentialAddress)]
[Description("ADR001")]
Home,
[ObjectDescription(InputAddressType.Unknown)]
[Description("ADR002")]
HomeSecondary,
[ObjectDescription(InputAddressType.CommercialAddress)]
[Description("ADR003")]
Business
}
The example above is a simple example, however if you imagine that there are over 200 of these enums, each having anywhere from 2 to 200 values you can see why having loads of switch/cases is unmaintainable. Also in the example there is a direct 1 to 1 map from input to output, however in the real world this is a rarity.
|
|
|
|
|
|
Initially I did consider XSLT, however the input XML is a rather interesting example of XML usage, so creating the XSL transform would have been extremely convoluted.
As an example the input XML is entirely attribute based and attribute values and presence depend on the value and presence of other attributes. So for example these two samples represent two different people (customer, staff)
|
|
|
|
|
There are limitations on what types of values may be passed to attributes.
Generally, only strings and numerics. Even enum values have to be cast to their underlying type (int, short, etc.).
|
|
|
|
|
But you're using Reflection on each call which is very slow, better to read them once and cache the results (after all the values aren't changing).
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
