C# Discussion Boards - CodeProject

kalyan_241630-Mar-07 0:35

30-Mar-07 0:35

class1
{
void function()
{
}
}
class2
{
void funtion()
{
}
}
static void main()
{
class1 c=new class1()
class2 c1=(class1)c;
}
this is all i know which was asked by my friend...
bye

Re: object oriented doubt

Colin Angus Mackay30-Mar-07 1:24

Colin Angus Mackay

30-Mar-07 1:24

kalyan_2416 wrote:
this is all i know which was asked by my friend...

Then you might want to get your friend to post here because that does not give enough information.

Your solution might involve using an interface, abstract class, virtual methods or a number of other possibilities. However, without knowing more it would be pointless to try and give an answer.

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Re: object oriented doubt

Christian Graus30-Mar-07 3:18

Christian Graus

30-Mar-07 3:18

FOr this to work at all, class2 needs to derive from class1. It doesn't matter if the functions in both classes are the same, if they have no inheritance relationship, you simply cannot cast them.

class1
{
public void Foo();
}

class2
{
public void Foo();
}

This code does not provide classes that can be cast to each other. There is no relationship.

public class1
{
public void Foo();
}

public class2 : class1
{
}

NOW class2 is of type class1. You can do this:

class2 c = new class2();
class1 c1 = (class1)c;

Note some differences :

1 - I cannot make a class1 into a class2, it is NOT a class2. class2 IS a class1, but it is more than that ( although I have not added any methods, it's automatic ).

2 - There was no need to cast c into a class2, it IS a class2. I am not sure if I needed to cast at all, I did just to be safe.

Another thing: You should really never do this:

class2 c2 = (class2) c;

This can throw exceptions at runtime. Instead, do this:

class2 c2 = c as class2;

This will assign c2 in all instances, if the cast fails, it will assign it as null. So, you add a check for null before you continue, to see if the cast was valid.

if (c2 != null)
{
// cast was valid.
}

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

filtering data for dataset that is bound to grid

JacquesDP29-Mar-07 23:58

JacquesDP

29-Mar-07 23:58

Hi all,

I have a dataset that gets filled with data from a xml file. That dataset is bound to a datagridview, how can I filter the dataset so that the datagridview only displays the relevant information.

Thanks in advance

He who laughs last is a bit on the slow side

Re: filtering data for dataset that is bound to grid

gauthee30-Mar-07 0:08

gauthee

30-Mar-07 0:08

string strConnectionString, strQueryString;
strConnectionString = "Provider=SQLOLEDB;Data Source=local;" +
"Initial Catalog=Northwind;Trusted_Connection=Yes;";
strQueryString = "SELECT CustomerID, CompanyName, ContactName, " +
"Phone, City, Country FROM Customers";
OleDbDataAdapter daDataAdapter = new OleDbDataAdapter(strQueryString, strConnectionString);
DataTable tblDataTable = new DataTable();
daDataAdapter.Fill(tblDataTable);
DataRow[] foundRows = tblDataTable.Select("Country = 'USA' AND City <> San Francisco'");
foreach (DataRow row in foundRows)
MessageBox.Show(row["CustomerID"].ToString() + " - " + row["ContactName"].ToString()+" - " + row["Country"].ToString());

for more info:
http://www.c-sharpcorner.com/UploadFile/raghavnayak/DataSetsIn.NETP212032005014116AM/DataSetsIn.NETP2.aspx" target="_blank" title="New Window">^]

Gautham

Re: filtering data for dataset that is bound to grid

JacquesDP30-Mar-07 0:13

JacquesDP

30-Mar-07 0:13

The dataset gets filled from a xml file. So I use dataset.readXML(string filename)

He who laughs last is a bit on the slow side

Re: filtering data for dataset that is bound to grid

kalyan_241630-Mar-07 0:39

kalyan_2416

30-Mar-07 0:39

datatable.Select("Condition")
to filter rows in a datatable in dataset

Re: filtering data for dataset that is bound to grid

JacquesDP30-Mar-07 1:20

JacquesDP

30-Mar-07 1:20

Thanks for the quick reply

I have a column name KEY, so I want to let the user type the KEY value in a textbox, then the grid must display all matches with that textbox value in the KEY column. How will the condition look for that?

He who laughs last is a bit on the slow side

Re: filtering data for dataset that is bound to grid

gauthee30-Mar-07 1:34

gauthee

30-Mar-07 1:34

Gautham

Some data Decrypt to return error Length of the data to decrypt is invalid

alpaslanaykovan29-Mar-07 23:57

alpaslanaykovan

29-Mar-07 23:57

Hi Everyone;
I try data dec&enc. small length of data is success but long size of data to return error Length of the data to decrypt is invalid.
Ex.

Encrypt data : 123465
up sample is decrypting no problem
Encrypt data "sample@sample.com"
this value decrypting is return error Length of the data to decrypt is invalid;

What is the problem

Everyone thanks

Re: Some data Decrypt to return error Length of the data to decrypt is invalid

Ennis Ray Lynch, Jr.30-Mar-07 4:04

Ennis Ray Lynch, Jr.

30-Mar-07 4:04

Block decryption ciphers require that the block size be correct for the cipher to work.

File Not Found

Inheritance and reflection

Russell Jones29-Mar-07 23:15

Russell Jones

29-Mar-07 23:15

I've got an abstract base class containing a guild field called _id.

I've derived some classes from my base class.

1 class has overridden the _id field and one hasn't.

My problem is that the object that doesn't override the _id field fails on the SetValue() call with Field == null so i get 'Object reference not set...'

public static void InjectID(Guid id,AbstractBase dataObject)<br />
{<br />
   //Type abstractBaseType = typeof(AbstractBase);<br />
   Type abstractBaseType = dataObject.GetType();<br />
   FieldInfo Field = abstractBaseType .GetField("_id");<br />
   Field.SetValue(dataObject, id);<br />
}<br />

The commented out line was my original code and the line below it was an attempted fix, but both behave in the same way.

Is there a way of getting to the fields defined in a base class?

Thanks

Russell

Re: Inheritance and reflection

Stefan Troschuetz29-Mar-07 23:36

Stefan Troschuetz

29-Mar-07 23:36

Is the _id field a public field? If not the GetField method cannot find it, since it is only looking for public fields with the given field.
To find private fields use the GetField overload that takes an additional bitmask of one or more BindingsFlags e.g.

abstractBaseType.GetField("_id", BindingFlags.NonPublic | BindingFlags.Instance);

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Rick Cook

www.troschuetz.de

Re: Inheritance and reflection

Russell Jones30-Mar-07 0:00

Russell Jones

30-Mar-07 0:00

damn, that works. I don't understand why the one that overrides it worked fine though.

Thanks for the suggestion. All my constructors are called like that, got thrown of the scent by the object that worked.

Thanks again

Russ

Re: Inheritance and reflection

DavidNohejl29-Mar-07 23:59

DavidNohejl

29-Mar-07 23:59

Russell Jones wrote:
Is there a way of getting to the fields defined in a base class?

base._id

I am not sure what are you doing here.

Are you using reflection because _id is private? Why not use protected virtual method/property? Is InjectID method of AbstractBaseClass?

"Throughout human history, we have been dependent on machines to survive. Fate, it seems, is not without a sense of irony. " - Morpheus
"Real men use mspaint for writing code and notepad for designing graphics." - Anna-Jayne Metcalfe

Re: Inheritance and reflection

Russell Jones30-Mar-07 0:40

Russell Jones

30-Mar-07 0:40

I'm writing a factory class that populates the objects from a database.

The id field has a public get accessor but no set accessor for obvious reasons. The object is not defined in the same project as the datafactory so I can't use internal to get to it.

InjectID is in the abstractFactoryBase class from which my databasefactory is derived.

Probably a crazy way to design an app but it's working the way i want with that last change and so far it seems very clean to use.

Russell

Re: Inheritance and reflection

DavidNohejl30-Mar-07 0:54

DavidNohejl

30-Mar-07 0:54

I knew there's more to it, but couldn't get the picture Smile | :)

Russell Jones wrote:
The id field has a public get accessor but no set accessor for obvious reasons. The object is not defined in the same project as the datafactory so I can't use internal to get to it.

There is attribute that does that. InternalsVisibleToAttribute[^]. Little brutal tho.

Re: Inheritance and reflection

Russell Jones30-Mar-07 2:14

Russell Jones

30-Mar-07 2:14

Wow, i don't believe such an attribute exists.

That seems wrong on so many levels,

Brutal seems a very good description

Russell

Problems when removing from ListBox

sinosoidal29-Mar-07 22:56

sinosoidal

29-Mar-07 22:56

Hi,

I'm creating something looked like the development enviorment in Visual Studio.

I have a panel with a listbox for "Activities".

I also have a panel with properties to change those activities properties.

I'm working on the deletion of activities but i'm having problems with the listbox.

i have the following two functions

<br />
private void lbActivities_SelectedIndexChanged(object sender, EventArgs e)<br />
        {<br />
            if (lbActivities.Items.Count!=0)<br />
            {<br />
                selectedActivityName = lbActivities.SelectedItem.ToString();<br />
                selectedActivityIndex = activities.FindIndex(withName);<br />
<br />
                pgProperties.SelectedObject = activitiesPropertyBags[selectedActivityIndex];<br />
            }<br />
        }<br />

This is a event for the listbox item change.

Well, i use two global variables to keep track of the selected item name and index. I also use a list to store my activities.

(is this stupid? could i use the listbox to do the same as the list, and avoid the use of two different structures?)

And here i have the code for deletion:

<br />
if (lbActivities.Items.Count != 0)<br />
            {<br />
                if (selectedActivityIndex == 0) {<br />
                    selectedActivityIndex = (lbActivities.Items.Count - 1) - 1;<br />
                    lbActivities.SelectedItem = lbActivities.Items[selectedActivityIndex];<br />
                }<br />
                else {<br />
                    selectedActivityIndex = lbActivities.SelectedIndex - 1;<br />
                    lbActivities.SelectedItem = lbActivities.Items[selectedActivityIndex];<br />
                }<br />
<br />
                lbActivities.Items.Remove(selectedActivityName);<br />
                activities.RemoveAt(activities.FindIndex(withName));<br />
            }<br />
        }<br />

The problem is that when the lbActivities.Items.Remove(selectedActivityName); is executed, the SelectedIndexChanged callback is called, and occurs an exception in the following instruction:

selectedActivityName = lbActivities.SelectedItem.ToString();

This happens even after i wrote the code above, which trys to change the selected item in order to avoid the selection of non existent item.

Any tips?

Thank you very much,

Nuno

Re: Problems when removing from ListBox

Russell Jones29-Mar-07 23:30

Russell Jones

29-Mar-07 23:30

you could set a bool _deletion in progress when you start doing the delete. In the selectedindex changed look for that flag and exit after changing it back to false.

The temptation with a lot of this code is to stick your list into a listbox and use it to maintain your collection. I always try not to do this as i find it leads to logic that is very hard to disentangle from presentation code. It may take more effort to maintain code this way at the start but later on you'll be glad of the separation if, for instance, you want to switch to using a treeview instead.

HTH

Russ

Re: Problems when removing from ListBox

sinosoidal30-Mar-07 0:40

sinosoidal

30-Mar-07 0:40

Hi,

Thx for the reply.

I managed to solve the problem setting selectedItem to null.

Thx,

Nuno

Creating a custom Vista HotFix INstaller..plz help

ke3p_up29-Mar-07 22:34

ke3p_up

29-Mar-07 22:34

hi guys

there's probably others way of installing 2 or more HotFixes on Vista, but i've decided that I'm going to write a program in C#, one that:

1 - will ask you to add the Htofixes to be installed
2 - Will send each of those Hotfixes to CMD.eXE in format of
eg : START /WAIT Windows6.0-KB931675-x86.msu /QUIET /NORESTART

but i'm already stock. i can't figure out to send a command such the one above to cmd.exe. i also have to wait til cmd returns from wat its doing before i can send the other command to it . How cam i do that? plz help

thanx

Re: Creating a custom Vista HotFix INstaller..plz help

stancrm30-Mar-07 0:55

stancrm

30-Mar-07 0:55

How about using

Process.Start(@"START /WAIT Windows6.0-KB931675-x86.msu /QUIET /NORESTART");

?

Re: Creating a custom Vista HotFix INstaller..plz help

ke3p_up30-Mar-07 2:00

ke3p_up

30-Mar-07 2:00

[correction]:

i tried:
Process.Start("CMD",@"START /WAIT C:\\Downloads\\Windows6.0-KB931675-x86.msu /QUIET /NORESTART");

but instead of the command been applied through CMD, i get
"Visual Studio 2005\Projects\WindowsApplication
2\WindowsApplication2\bin\Debug>" in CMD?

Also how is it possible to detect when CMD has returned from applying the patch? for example if i have 5 patches to apply, if i put on through CMD , i need to wait until that patch is done, and once thats done, only then i want the second patch to be appied. how can i detect that?

thanx

Re: Creating a custom Vista HotFix INstaller..plz help

ke3p_up30-Mar-07 2:45

ke3p_up

30-Mar-07 2:45

ok got that fixed Smile | :)

it should be :

Process.Start("CMD",@"/C START /WAIT C:\\Downloads\\Windows6.0-KB931675-x86.msu /QUIET /NORESTART");

Now how can i detect when CMD has finished processing the current patch and is ready so i can send the other patch to CMD then? thanx

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