C# Factory Pattern - C# Discussion Boards

27-Nov-07 13:43

Err... the design pattern to use is the Factory Pattern, if you want to use the Factory Pattern, that is...

As to the how to, I've found this a worthwhile (if not free) resource:

http://www.dofactory.com/Patterns/PatternFactory.aspx[^]

"On one of my cards it said I had to find temperatures lower than -8. The numbers I uncovered were -6 and -7 so I thought I had won, and so did the woman in the shop. But when she scanned the card the machine said I hadn't.

"I phoned Camelot and they fobbed me off with some story that -6 is higher - not lower - than -8 but I'm not having it."
-Tina Farrell, a 23 year old thicky from Levenshulme, Manchester.

Re: C# Factory Pattern

Jeffrey Walton27-Nov-07 14:50

Jeffrey Walton

27-Nov-07 14:50

Hi Martin,

Thanks. It's been too long since I had a Design Patterns class (and I cannot find the text book from college).

In the examples, it seems Main() must know 'a priori' what classes to instaniate. Is this knowledge included in the Factory, or is this a poor example?

Perhaps if I briefly explain my problem domain, it will help cut to the chase.

Jeff

I parse a flat text file. Each token will become a distinct object. So I would like to:

Token t = NextToken()               // Base Class
Object o = Factory.CreateObject(t)  // Static method

o will then be Type1, Type2, Type3, etc. Factory::CreateObject would be a message cracker:

if( t.field = 1 ) { return new Type1(t); }
...
if( t.field = n ) { return new TypeN(t); }

Re: C# Factory Pattern

martin_hughes28-Nov-07 3:19

Simple question about ending loops

28-Nov-07 3:19

Hey Jeff,

I had to have a good long think about what you're trying to do (I'm no pattern guru myself, which is why I recommend DoFactory) and came accross this article which might prove useful:

http://www.codeproject.com/cs/design/csdespat_4.asp[^]

and this one:

http://www.codeproject.com/useritems/BuilderPattern.asp[^]

falles0127-Nov-07 12:25

falles01

27-Nov-07 12:25

I have a problem where I've got a large amount of nested if statements.
they were all working and executing the correct numbe of times until I added some loops at the start.

The debugger is showing that it executes the first section and then starts again without going to the next condition. I know I have to change the condition maybe. This is the first section that gets executed continuously. Obviously there will always be rows, but the rest of conditions say, if checkedbox is ticked, or combobox is selected bla bla, so I can't see why (if I select a combobox item and click search, it is not executing). Is there a way of telling the code that you want to end the loop after all the entries in the database have been covered? Make sense?

foreach (DataRow row in dsapps.Tables[0].Rows)<br />
                {<br />
<br />
                    if (row["EmployeeID"].ToString().Equals(EmployeeID.ToString()) == false)<br />
                    {<br />
                        if (EmployeeID > 0)

martin_hughes27-Nov-07 12:39

27-Nov-07 12:39

Missing a curly brace somewhere? How about an errant ";"?

falles0127-Nov-07 12:44

falles01

27-Nov-07 12:44

Thanks yes I worked it out. It was just a silly curly brace. i wasn't missing one as such, I just had to move them around.
Wasn't worth the question. Sorry about that.

Colin Angus Mackay27-Nov-07 14:14

Colin Angus Mackay

27-Nov-07 14:14

falles01 wrote:
It was just a silly curly brace. i wasn't missing one as such, I just had to move them around.
Wasn't worth the question. Sorry about that.

Don't worry about it. There has been many a time I've sat in front of a compiler in despair at the apparently cryptic error message only to discover after I've asked someone else to have a look they spotted in seconds the missing semi-colon or some such trivial detail.

Upcoming FREE developer events:
* Developer Day Scotland

My website

martin_hughes27-Nov-07 14:52

Automatically generate Release Notes from code

27-Nov-07 14:52

As Colin says - easy mistake to make.

kozu27-Nov-07 10:31

kozu

27-Nov-07 10:31

Hi,
I need to generate release notes from code, but if I use XML comments to let the parser generate the html for me the notes will keep adding up. Is there a way to tell the parser to parse only the tags that have a certain value? Something like: if I want the release notes for today's build, I want to parse only the tags that have today's date as a value.
If this is not doable, is there any other way of getting release notes from code without keeping a separate document that someone would have to manually update after each build?
thanx

Cross post. Please ignore this thread.

Pete O'Hanlon27-Nov-07 10:56

Pete O'Hanlon

27-Nov-07 10:56

See title.

Deja View - the feeling that you've seen this post before.

My blog | My articles

Re: Cross post. Please ignore this thread.

Paul Conrad27-Nov-07 12:23

Paul Conrad

27-Nov-07 12:23

Alright, moving along to next post Laugh | :laugh:

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

populating a listview from another class

kenwen27-Nov-07 9:55

kenwen

27-Nov-07 9:55

Hi, I am a an absolute novice to C# and have just about managed to get my first(simple) project off the ground. I am now trying to populate a listiew on a form from data retreived from Sql server in another class but I just get the message The listview does not exist in the class or namespace.

If I place the code in the form it works but not in a different class can some help please?

regards
kenwen

pmarfleet27-Nov-07 10:19

pmarfleet

27-Nov-07 10:19

The ListView control has to be placed on a form. The class for the form is therefore aware of the existence of the control. This is why you can write code that references the control in the form's code-behind file. However other classes you create don't know anything about the ListView control unless you pass an object reference to it in one of its properties or methods.

I'm not sure what you are trying to do. Perhaps if you posted a bit of your code your requirements might make more sense.

Paul Marfleet

"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush

kenwen27-Nov-07 10:37

kenwen

27-Nov-07 10:37

Thanks Paul, Here is the bit of code that opens SQL and the recordset

using System;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace LoomScheduler
{
///

/// Summary description for LoadLooms.
///

public class LoadLooms
{
private System.Data.SqlClient.SqlDataReader SqlReader;

public LoadLooms()
{

SqlConnection myConnection = new SqlConnection("user id=username; password=sa;" +
"server=Brintons_NT03; Trusted_Connection=yes; database=LoomSchedules; connection timeout=30");

SqlCommand LoadLooms = new SqlCommand("Select LoomNo, Type," +
"ShortType From tblLoomMastShortVersion Where Plant = '12'" +
"Order By ShortType, LoomNo",
myConnection );

cnSchedule.Open();

SqlReader = LoadLooms.ExecuteReader();

while(SqlReader.Read())
{
ListViewItem lvi = new ListViewItem();

lvi.Text = (SqlReader["LoomNo"].ToString());

// Here I want to add each record to a listview called lvTopLooms on a form called frmMain
//lvTopLooms Items.Add(lvi.Text);

}

}
}
}

pmarfleet27-Nov-07 10:49

pmarfleet

27-Nov-07 10:49

As I previously explained, you need to pass a reference to your ListView control to your class. Change the declaration of your constructor to:

public LoadLooms(ListView lvTopLooms)

and pass a reference to your control from the code in your form that instantiates LoadLooms.

Your code looks a bit odd though. I'm don't think it's good practice to pass references to controls around to other classes. It would probably be better if your class simply provided a method to retrieve data from your database. Your form class could then call this method to get the data to populate the ListView control and you would'nt have to pass a reference to this control anywhere. Also, you're doing stuff in the class constructor that would be better suited to being placed in a method. The class constructor should really only be used for the initialization of variables, resources etc.

Paul Marfleet

"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush