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I tried to build using your suggestion to set SPECIFIC VERSION to FALSE, but it still failed.
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Wait a second... Are the lines in correct order? Shouldn't it be:
using Oracle.DataAccess.Client;
namespace Gnf.Utils.Oracle
{
...
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Yes!!!! That worked! But I don't understand.
I didn't change that code at all, and I'm sure the previous developer built it successfully.
I don't understand why I have to declare this particular thing outside of the namespace, while the others can be defined inside.
using Oracle.DataAccess.Client;
namespace Gnf.Utils.Oracle
{
using Gnf.Utils.Data;
using System;
using System.Collections.Generic;
using System.Data;
using System.Runtime.InteropServices;
using System.Threading;
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I'm not sure. Perhaps you have two namespaces in the file and if the the other one also wants to use classes from Oracle.DataAccess.Client, the using directive would be out of scope, just a guess since I actually never use using directive. I always like to add full namespace to a class definition.
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Well, its a standard practice to use Using before declaring Namespace.
The compiler need to know what references to use (Using) before it can compile the namespace function map.
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So I'm coding in .NET (C#), under Visual Studio, and getting some numbers in string format and converting them to double.Parse to doubles. However, it only works if the number strings first have the . replaced with a ,
How can I make the double.parse command give me decimals delimited with dots , not commas?
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Have you checked setting for the local computer? In Vista the formatting is set in the Regional and Language options dialog from the control panel
only two letters away from being an asset
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Thanks, good idea, however, I just checked and the decimal separator is already defined as the dot.
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use this:
double dummyOut = new double();
System.Globalization.CultureInfo cultureInfo = new System.Globalization.CultureInfo("en-US", true);
Double.TryParse(anyString, System.Globalization.NumberStyles.Any, cultureInfo.NumberFormat, out dummyOut); }
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Using generics and interfaces in .net, it's possible to design a class so that a particular method name can invoke a number of different methods, based upon the type of a passed-in parameter. For example:
Class DoItMagic
Interface iAct(Of T)
Sub Act(ByVal param As T)
End Interface
Public Shared Sub exec(Of T)(ByVal target As iAct(Of T), ByVal param As T)
target.Act(param)
End Sub
Public Shared Sub hitEverything(Of T, U As DoItMagic.iAct(Of T))(ByVal theEnum As IEnumerable(Of U), ByVal theParam As T)
For Each thing As U In theEnum
exec(Of T)(thing, theParam)
Next
End Sub
End Class
Class DoItTarget
Implements DoItMagic.iAct(Of param1), DoItMagic.iAct(Of param2)
Class param1
End Class
Class param2
End Class
Public Sub Act_param1(ByVal param As param1) Implements DoItMagic.iAct(Of param1).Act
End Sub
Public Sub Act_param2(ByVal param As param2) Implements DoItMagic.iAct(Of param2).Act
End Sub
End Class
Class DoItTest
Dim firstParam As DoItTarget.param1
Dim secondParam As DoItTarget.param2
Dim L As List(Of DoItTarget)
Sub go()
DoItMagic.hitEverything(Of DoItTarget.param1, DoItTarget)(L, firstParam)
DoItMagic.hitEverything(Of DoItTarget.param2, DoItTarget)(L, secondParam)
End Sub
End Class
This approach seems to work out pretty elegantly. The first hitEverything will call iAct(of Param1) on each element of the list; the second will call iAct(of Param2). Additional methods may be added by simply creating new classes and adding interface iAct(of eachNewClass), without any need to change anything in DoItMagic.
My questions:
- Are there any performance implementations with creating empty classes that are used as method selectors rather than as distinct ways of holding data (e.g. there might be a number of different classes that hold a single integer, but select different methods).
- Does invoking methods via generics pose any performance problems in cases where everything can be type-checked at compile time?
- What would be the performance implications in cases where things couldn't be checked until run-time (e.g. if a list holds a number of elements, not all of which will support any particular iAct(of type).
- Is this overall approach a brilliant idea, crazy idea, or somewhere in between?
I like the way this approach seems to work, but I would be very sad if I developed a lot of code with it and discovered that while it performed well in initial testing it sometimes dogged in real applications. Any thoughts?
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Here is my experience.
You will have overall performance boost by using OOPS and Generics.
I have a project where I have used many classes and many generics almost in the same way as you are doing it. We did a performance test by bombarding with several request to the project and it performed better as against using OOPS without generics (many many classes and hence objects).
Generics gives the ability to precast and late binding, and also once loaded in memory it stays there to be consumed upon request.
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Why not just use the build in List< U>.ForEach(instance.Act)?
If you need to use IEnumerable, then a trivial extension method would work:
static void ActOnABunchOfStuff< U>(IEnumerable< U> bunch, Action< U> action)<br />
{ foreach(var stuff in bunch) action(stuff); }
Use with:
int[] foo = {1,2,3,4,5};<br />
ActOnABunchOfStuff(foo, doItTarget.Act);
VB-i-cise it at your leisure 
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Why not just use the build in List< U>.ForEach(instance.Act)?
Are you assuming Action< U> is a delegate for a void function that takes a single parameter of type U? I'm not terribly familiar with C# syntax, and I don't see any declaration for Action.
Also, I would guess that the last statement was supposed to be ActOnABunchOfStuff< integer>(foo, doItTarget.Act); but the board gobbled up what it thought was a tag?
If all the items in the list are of the same concrete type, I suppose that approach would work, at the expense of generating lots of silly little wrapper functions. Maybe that's no worse than generating silly little classes, but the generics approach I describe could offer another benefit that might be harder to achieve without generics: one could have a list of objects and do an enumerated invoke with something like if typeof(it) is iAct(of T) Then CType(it, iAct(of T)).Act(whatever). Not sure what the performance of that would be, but it would allow one to achieve a form of event handling without requiring every item to create a delegate for every different event that it supports. One could do such 'typeof/is' testing in a wrapper function, but that would seem a bit inelegant.
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With that last statement, the type parameter U is inferred (at least in C#) from the type of foo (which is as you say an int).
System.Action(Of T) is in mscorlib, and has the signature you guessed. Theres also a couple of others with extra parameters.
I may have got a little confused with what you are trying to achieve. Invoking a method on each instance in a list, passing the same parameters?
I would use the equivalent of listOfThings.ForEach(x => x.SomeMethod(p1,p2,p3,etc));. This might be a little messy in VB though.
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The basic concept is that I have an class for objects that contain a number of objects that the class doesn't really understand in detail (an iEnumerable is a common example of such a thing, though hardly the most sophisticated) and I would like for code outside the class to be able to invoke methods on some or all of the objects within, generally passing the same parameters to all. In some regards similar to delegates, except (1) delegates are hard-wired for particular method-object pairs, and (2) there is no need to hold the method info for a delegate without holding a hard reference to the object.
One class I created using this approach (which seems to work nicely, though I haven't benchmarked its behavior in a program with hundreds of classes) manages something like event subscription, but using weak references. Any number of objects may subscribe to a 'publisher' object; performing .Exec(of T) on the publisher object will cause it to call function iAct(of T).Act on any subscribed object supporting interface iAct(of T). Subscription and unsubscription are O(1), non-locking, and thread-safe; an object will be unsubscribed if it (1) gets garbage-collected, (2) uses the Unsubscribe method of the Subscription object returned when the object originally subscribed, or (3) one of its iAct(of T) functions returns True when invoked.
My original intended application for this class would be in an application where a number of forms have controls that affect the same properties and should thus all affect each other. While events provide a nice way to achieve much of that functionality, all the forms need a reference to an object that will support all of the events they need. If new events are added, the linking object will have to be extended to support them. Worse, using events creates the possibility of memory or resource leaks if any objects don't get properly disposed. Finalizers won't do any good if delegates keep objects alive forever.
Using my actionLink class avoids these difficulties; if I create a class called e.g. volumeChangedParam, I can call Exec(of volumeChangedParam) on my event publisher object and any subscribed object that supports an iAct(of volumeChangedParam) will have its iAct(of volumeChangedParam).Act function called. The actionLink class doesn't have to know anything about volumeChangedParam or any of the other classes it works with; additional classes could be added to support other operations.
All this stuff seems to work fine, but I wouldn't want to engineer too much of a system around it if it turned out that, e.g. the .net framework performs wonderfully when an application uses less than a certain number of classes, and starts dogging badly if the application uses more.
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Trying to build a dynamic datatable and not sure how to define a blob column.
eg
DataTable dt = new DataTable();
dt.Columns.Add("uid");
dt.Columns.Add("test", Type.GetType("System.String"));
dt.Columns.Add("MyBlob",???
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DataTable dt = new DataTable();
dt.Columns.Add("uid");
dt.Columns.Add("test", Type.GetType("System.String"));
dt.Columns.Add("MyBlob",Type.GetType("System.Object"));
Just a guess, haven't run it through the compiler 
I are troll 
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If you're going to store the blob into database, write the contents to a file etc, I think it would be easiest to use byte[], so you could write:
dt.Columns.Add("MyBlob", typeof(byte[]));
Just a sidenote, you could use typeof operation instead of using Type.GetType("...") like:
dt.Columns.Add("test", typeof(string));
One advantage is that if you make a typo, the compiler sees it and won't compile. If you write
dt.Columns.Add("test", Type.GetType("System.Striiiiiiing"));
it will compile but you will get an exception at runtime.
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you can use Object, string or even byte[] type.
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First of all I need to say I'm not an expert .NET programmer
I'm working in a Windows environment (using VB.NET) and I need to launch
an X Command over a Linux machine. On the Windows environment I have installed
an X emulator.
I found that the SharpSSH library from Tamir Gal web site should solve my problem, but
testing the example "SshExeTest" I cannot visualize any graphical interface (e.g. Xclock display)
while it seems to be possible as reported in the README.txt file at the SharpSsh example web page
Could someone provide me information about this topic and (possibly) a code snippet in order to
properly execute the X command?
Many many thanks...
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Hi Guys,
I've got a custom VirtualPageProvider setup and running locally on Cassini, but when i deployed it, i found i had problems with the virtual files. I have added tracing and both the FileExists() method and GetFile() methods are called by pages that physically exist in the website (i.e. Default, Login) and are noted in the log, however, the virtual pages I'm trying to access never even hit the FileExists() method, and instead return a 404 error.
The file types are .wmv and .jpg, and i have tried including the following in my config file:
<add verb="GET,HEAD,POST" path="*.jpg" type="System.Web.StaticFileHandler" validate="true" />
<add verb="GET,HEAD,POST" path="*.wmv" type="System.Web.StaticFileHandler" validate="true" />
Without any success.
I have no idea what the hell is going on here, anyone got any ideas?
Regards
Tris
-------------------------------
Carrier Bags - 21st Century Tumbleweed.
modified on Monday, January 19, 2009 10:49 AM
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I assume you mean a VirtualPathProvider (not Page).
There is not enough info to help.
Things to try if you haven't already:
1. Write an empty wrapper for all VirtualPathProvider methods and set a breakpoint in each, check which, if any are called.
2. Write a simple IHttpHandler to use as the static file handler, again set a breakpoint in ProcessRequest and follow it.
I had to do both to get my first vpp working.
I use System.Web.StaticFileHandler with vpp's and it works, StaticFileModule however does not.
...cmk
The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying.
- John Carmack
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Hi CMK,
I have made both a wrapper for the VirtualPath and an HTTP handler. The VPP gets hit by non virtual pages, but not for virtual pages. The Http handler does not get hit for virtual pages.
Regards
Tris
-------------------------------
Carrier Bags - 21st Century Tumbleweed.
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Other things to check:
You aren't using a url rewrite engine, or any IHttpModule, that isn't vpp aware, i.e. it's failing the request as file not found.
The static file isn't being handled by a handler earlier in the chain (earlier in the web.config file).
As mentioned i had to fiddle for a while to get things just right. In particular i return a merged VirtualDirectory from GetDirectory and merged CacheDependency from GetCacheDependency.
...cmk
The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying.
- John Carmack
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