Re: C# Class Inheritance - C# Discussion Boards

2-Feb-06 11:16

I have 4 classes. Class A is derived from System.Object, class B is derived from ArrayList (the collection class), class C and class D are derived from class B. All 4 classes of mine have ToString methods that each show a different thing. I used the 'override' reserved word in each declaration to replace the funcionality of the inherited method. I have a form which has a drop-down listbox that utilizes the ToString methods of classes' C and D only. I also have a TreeView that shows all 4 classes in a tree diagram, consider that class B and D are root items in the tree view and only contain objects of type A and C respectively.

The problem is classes A and B work 100% fine, but only those two.

However, classes C and D are the problem. In the form with the list box, I add objects of type class C using dlg.listbox.Add(new class C("some text", somevalue)); before showing the form. Class C has that overridden ToString method that returns a special string based on that string and that value given to it. On runtime, the box simply says (Collection) instead of what it should.

Later, the same class C object shows up in the tree view, but instead of seeing the same (Collection), you see some text but only that text. Somewhere the object is returning that custom text element and not the value, and the ToString method for class C incorporates both like I mentioned earlier.

I don't know how to fix this. I put breakpoints on every ToString method and the first two classes trigger fine but C and D's are never used. The project is too complex to just paste it all so if you have an idea and need more info, just ask and I'll be glad to answer.

Guffa2-Feb-06 11:21

Guffa

2-Feb-06 11:21

What more do you have in the C and D classes? It seams like the listbox reads the value directly from a member. Do you have any public members that might be used by the listbox?

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b { font-weight: normal; }

LighthouseJ2-Feb-06 11:44

2-Feb-06 11:44

class B has a String and a custom class type, C has a number and D has nothing more than the String and custom class intended for B. I didn't mention it before but I know about and utilized the base constructor.

It was my understanding that I could add objects to the listbox Items collection and when the listbox is run, it shows strings from the ToString method from the specific object. The only other method I have besides class C's ToString is its constructor and a method used to gather TreeNode-derived objects from the items in its collection.

Guffa2-Feb-06 22:19

Guffa

2-Feb-06 22:19

Make sure that you haven't missed the override keyword on any of the ToString methods. The Object.ToString method is virtual, but if you don't override it, you will be creating a non-virtual method that will only be reachable when refering to the object using a reference of the specific type. When referenced as an object, the virtual method will be used instead.

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b { font-weight: normal; }

LighthouseJ3-Feb-06 4:34

3-Feb-06 4:34

I double checked that several times and I did give all four instances of ToString the override keyword. It's very frustrating that it keeps happening. I also added marks in each ToString to display what class the ToString is being called from and the first three classes are fine, it's just that last one class can't show it's ToString in the combo box like it should.

I'll keep hammering at it though, I know it's worked before. I figure I might have a "base.ToString()" instead of a "this.ToString()" or something set wrong like that.

Ravi Bhavnani2-Feb-06 11:24

Ravi Bhavnani

2-Feb-06 11:24

LighthouseJ wrote:
the first two classes trigger fine but C and D's are never used.

I believe you may need to make B's ToString() virtual.

/ravi

My new year's resolution: 2048 x 1536
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ravib(at)ravib(dot)com

LighthouseJ2-Feb-06 11:45

2-Feb-06 11:45

I thought about that before and tried it but there was no difference in the outcome in runtime.

malharone2-Feb-06 11:37

2-Feb-06 11:37

LighthouseJ wrote:
The project is too complex

Here's a simple solution.. has the same class hierarchy as you described.. and it shows the .ToString() values. (I hope you're not confusing ListBox with ListView)

- Malhar

using System;<br />
using System.Drawing;<br />
using System.Collections;<br />
using System.ComponentModel;<br />
using System.Windows.Forms;<br />
<br />
namespace Malhar.ControlGallery<br />
{<br />
	/// <summary><br />
	/// Summary description for Form3.<br />
	/// </summary><br />
	public class Form3 : System.Windows.Forms.Form<br />
	{<br />
		private System.Windows.Forms.ListBox listBox1;<br />
		private System.Windows.Forms.Button Load;<br />
		/// <summary><br />
		/// Required designer variable.<br />
		/// </summary><br />
		private System.ComponentModel.Container components = null;<br />
<br />
		public Form3()<br />
		{<br />
			//<br />
			// Required for Windows Form Designer support<br />
			//<br />
			InitializeComponent();<br />
<br />
			//<br />
			// TODO: Add any constructor code after InitializeComponent call<br />
			//<br />
		}<br />
<br />
		/// <summary><br />
		/// Clean up any resources being used.<br />
		/// </summary><br />
		protected override void Dispose( bool disposing )<br />
		{<br />
			if( disposing )<br />
			{<br />
				if(components != null)<br />
				{<br />
					components.Dispose();<br />
				}<br />
			}<br />
			base.Dispose( disposing );<br />
		}<br />
<br />
		#region Windows Form Designer generated code<br />
		/// <summary><br />
		/// Required method for Designer support - do not modify<br />
		/// the contents of this method with the code editor.<br />
		/// </summary><br />
		private void InitializeComponent()<br />
		{<br />
			this.listBox1 = new System.Windows.Forms.ListBox();<br />
			this.Load = new System.Windows.Forms.Button();<br />
			this.SuspendLayout();<br />
			// <br />
			// listBox1<br />
			// <br />
			this.listBox1.Location = new System.Drawing.Point(8, 16);<br />
			this.listBox1.Name = "listBox1";<br />
			this.listBox1.Size = new System.Drawing.Size(176, 95);<br />
			this.listBox1.TabIndex = 0;<br />
			// <br />
			// Load<br />
			// <br />
			this.Load.Location = new System.Drawing.Point(192, 8);<br />
			this.Load.Name = "Load";<br />
			this.Load.TabIndex = 1;<br />
			this.Load.Text = "button1";<br />
			this.Load.Click += new System.EventHandler(this.button1_Click);<br />
			// <br />
			// Form3<br />
			// <br />
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);<br />
			this.ClientSize = new System.Drawing.Size(292, 266);<br />
			this.Controls.Add(this.Load);<br />
			this.Controls.Add(this.listBox1);<br />
			this.Name = "Form3";<br />
			this.Text = "Form3";<br />
			this.ResumeLayout(false);<br />
<br />
		}<br />
		#endregion<br />
<br />
		private void button1_Click(object sender, System.EventArgs e)<br />
		{<br />
			listBox1.Items.Add(new A());<br />
			listBox1.Items.Add(new B());<br />
			listBox1.Items.Add(new C("John", 4));<br />
			listBox1.Items.Add(new C("Lisa", 10));<br />
			listBox1.Items.Add(new D());<br />
		}<br />
<br />
		class A<br />
		{<br />
			public A():base()<br />
			{<br />
			}<br />
			public override string ToString()<br />
			{<br />
				return "Object of type A";<br />
			}<br />
		}<br />
		class B:ArrayList<br />
		{<br />
			public B():base()<br />
			{<br />
			}<br />
			public override string ToString()<br />
			{<br />
				return "Object of type B";<br />
			}<br />
		}<br />
		class C:B<br />
		{<br />
			string someStr;<br />
			object someVal;<br />
			public C(string text, object value)<br />
			{<br />
				someStr = text;<br />
				someVal = value;<br />
			}<br />
			public override string ToString()<br />
			{<br />
				return string.Format("Object of type C: {0}; {1}", (someStr==null?"-":someStr), (someVal==null?"-":someVal.ToString()));<br />
			}<br />
		}<br />
		class D:B<br />
		{<br />
			public D()<br />
			{<br />
			}<br />
			public override string ToString()<br />
			{<br />
				return "Object of type D";<br />
			}<br />
		}<br />
	}<br />
}

LighthouseJ2-Feb-06 11:53

EDIT MENU + CUT, COPY, PASTE

2-Feb-06 11:53

Actually, I was wrong and it's a combobox, but class B contains the string and a custom class, and C has an int. My class structure and ToString() method definitions are basically the same thing, you say yours works so I don't know what's different to not work.

emran8342-Feb-06 11:08

emran834

2-Feb-06 11:08

Hello,
In my Windows Form, I have almost 20 textboxes and editable controls. I was wondering is there any way i can apply Edit Menu (Cut, Copy, Paste, Select All) fetaures and MOUSE RIGTH CLICK MENU (CUT, COPY, PASTE, SELECT ALL) and SHORT CUT KEYs ( CTRL + C, CTRL + V, CTRL + X, CTRL + A) without writing code for each control seperately ? It is very boring and very hard to write code for each control, right ! So, I am pretty sure there must be an easy solution for that. So, would you please let me know if there is any solution to this kkind of boring task !!

thanks to all
Emran

Re: EDIT MENU + CUT, COPY, PASTE

J4amieC2-Feb-06 23:08

J4amieC

2-Feb-06 23:08

You do realise you can apply the same event handler to every textbox on a form right? For example, the KeyDown event

private void MyKeyDownEventHandler(object sender, KeyEventArgs e)<br />
{<br />
// do something<br />
}<br />
<br />
myTextBox1.KeyDown += new KeyDownEventHandler(MyKeyDownEventHandler);<br />
myTextBox2.KeyDown += new KeyDownEventHandler(MyKeyDownEventHandler);<br />
myTextBox3.KeyDown += new KeyDownEventHandler(MyKeyDownEventHandler);

Re: EDIT MENU + CUT, COPY, PASTE

emran8343-Feb-06 17:20

emran834

3-Feb-06 17:20

Hi J4amieC,
Thanks for your reply.

Yes, i realize that i can use same handler, but you see, in that handler i will have to use a very big list of if else statement for every text box, right ?

like,

if(txtbox1.Focused)
txtbox1.Copy();
else if(txtBox2.Focused)
txtbox2.Copy();
............

.................
...............
ekse if(txtboxN.Focused)
txtBoxN.Copy();

and then I will have to write same if else for CUT(), PASTE, SELECTALL,... right ? and I thought it s a very hard way to maintain codes and there must be some simple method solution for this purpose as this task is essential for everyone for any kind of application and there must be some way available for this task.

thanks and regards
Emran

Get a controll fully customized

Sasuko2-Feb-06 10:22

Sasuko

2-Feb-06 10:22

what is the best way to create a controll with my how drawing?
Can i use for it a bitmap at the place drawing it in GDI+?
(i ask this becouse i've tried to create a button using a panel then set as backgound an image loaded from the Hard disk, at the mouse action i get other images from an imagelist object, but i don't like this way futhermore on the on paint event i see this panel all black before to see the image)

Re: Get a controll fully customized

Ingo3-Feb-06 2:14

Ingo

3-Feb-06 2:14

Well if there is no image set, then just clear the control in the backgroundcolor you like, best use a property:

e.Graphics.Clear(BackgroundColor);
if (image != null) {
e.Graphics.Drawimage(...);
}

Greetings,
Ingo

------------------------------
An bug in a Microsoft Product? No! It's not a bug it's an undocumented feature!

To know which file was opened by an application.

yjoo93172-Feb-06 10:13

yjoo9317

2-Feb-06 10:13

Hi,
For example,
I am trying to know when I opened, say,'example.doc' word file or 'example.pdf' file.

I know msword or acrobat is running...
But how can we know which file was opened by msword or acrobat.

FileSytemWatcher looks like responding on only the events which changed file content.
Reading a file isn't an event reported by the watcher.

Process gave me module name but not the target file(doc or pdf file name).

Maybe I am missing some user32 functions.
But at this point, I don't know how to retrieve that information.

Many thanks in adance,

yjoo.

Re: To know which file was opened by an application.

malharone2-Feb-06 11:11

Re: To know which file was opened by an application.

2-Feb-06 11:11

FileSytemWatcher is watching for changes. When you open a file, the OS puts a virtual lock on the file but does actually modify the file. But when a file is saved, the FSW will trigger the modify event.

- Malhar

yjoo93172-Feb-06 11:26

yjoo9317

2-Feb-06 11:26

Thanks for reply...
Yes,I know we can detect any changes if made to a file.

In case of pdf file,
The file will unlikely change.
What I want is that,
if I know msword or acrobat(these are examples) is running,
then I want to know which file was opened by the application.

Thanks..

Re: To know which file was opened by an application.

Dave Kreskowiak2-Feb-06 15:40

Dave Kreskowiak

2-Feb-06 15:40

There is no easy little API call to make. This will require a black belt in Windows internals. Not all expose an API to tell you what files that app has open, and most apps don't expose any kind of API at all.

You'd have to enumerate the handles of the process you're interested in, be it Word or Acrobat Reader. The problem is this technique is not documented anywhere, source code for it is very sparse, and it's all written in C++. You can find an example buried in the source for a Task Manager Extension, found right here[^] on CodeProject.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Validation of WinForm Data

Wayne Phipps2-Feb-06 9:51

Wayne Phipps

2-Feb-06 9:51

Hi There,

I want to be able to validate data entered by a user onto a form.

Different fields will have different validation requirements.

As an example, a text box may only allow numeric, alpha or alpha numeric entry and/or may have limitations on length or value.

I thought about inheriting a control from one of the standard forms controls and adding the validation code required but was thinking that this would make the application heavier than necessary because certain fields only require certain validation.

I wanted a way to add validation only where required so thought of creating a validator object which could have various validationRule objects added as required.

The validator could respond to events like textChanged on a text box and where it would then check the rules that had been applied.

I thought that the validationRule object would be either abstract or impliment specific interface.

I like the GOF 'Chain of Responsibility' pattern as a way of getting the rule objects to respond to a message from the validator however, I don't know how to ensure that all the rule objects have received/responded to the message.

Does this concept make sense? Is this the best way to go about validating user input? Is this pattern appropriate in this example?

Your thoughts/ideas/comments appreciated.

Regards

Wayne Phipps
____________

Time is the greatest teacher... unfortunately, it kills all of its students
View my Blog

Pixel size of frame and control changed

xjsun2-Feb-06 9:35

xjsun

2-Feb-06 9:35

Hello,

I am having a very strange problem with my .NET/C# application and I need help here. Thank you very much.

The problem is that when I run my GUI program on one laptop (xp/sp2), the size of the frame and controls are somehome changed/stretched. I tried to adjust all sorts of windows settings but no help. I then brought the source code to the machine and run the .NET VS (1.1), what I found is that the size (pixels) of the frame and controls are changed automatically. I don't understand why it happens...Could anyone know about this issue?

Regards,
John

Re: Pixel size of frame and control changed

malharone2-Feb-06 11:15

Re: Pixel size of frame and control changed

2-Feb-06 11:15

Are you running an OS verion with Asian culture and/or using wide-screen monitor? (I had similar issue .. but couldnot find any relevant articles for the cause). I changed my entire UI to utilize docking (previously it used anchoring) and then UI problems disappeared.

- Malhar

xjsun7-Feb-06 8:09

xjsun

7-Feb-06 8:09

Thanks for the help. But I've found the cause of the problem and the solution (workaound) as well.

The cuase of the issue is by changing the DPI setting (under Display -> Settings -> Advanced). When the DPI is set to 120 instead of default 96, some of the controls will get this problem, ie. the picture box. To fix it, there is a workaround to add the following code after the InitializeComponent() in formMain().

SizeF sf = Form.GetAutoScaleSize (this.Font);
this.AutoScaleBaseSize = sf.ToSize ();

John

Re: Pixel size of frame and control changed

malharone7-Feb-06 8:11