Windows Forms

1-Apr-10 2:12

Hello,

In an interview asked to me that,

Tell me an real time use of an interface.

Apart from importing namespace is there any use for "Using" keyword in C#.net.

Could anybody can answer these question. I would be very thankful to you

Regards
Azeem

Eddy Vluggen1-Apr-10 2:26

1-Apr-10 2:26

Ahamed Azeem wrote:
Tell me an real time use of an interface.

The question is rather unclear; it sounds as if you're requesting for an example of an interface in a real-time environment, but I'm going to guess that you want a practical example where we use interfaces. How about IDbConnection and IDbCommand?

Ahamed Azeem wrote:
Apart from importing namespace is there any use for "Using" keyword in C#.net.

Yup, both as a naming-alias for existing namespaces, as well as defining scope for a class that implements IDisposable.

I are Troll Suspicious | :suss:

Ahamed Azeem1-Apr-10 2:33

1-Apr-10 2:33

Thank your for your reply.

Why do we want to go for interfaces rather than normal method definition.

Your second answer is not clear to me. Could you pls explain more

Regards
Azeem

Eddy Vluggen1-Apr-10 3:33

1-Apr-10 3:33

Ahamed Azeem wrote:
Why do we want to go for interfaces rather than normal method definition.

Mostly to prevent thight coupling, but there may be other reasons. An interface just says how the "normal method definition" should look, it doesn't contain any implementation; that means that if a class implements an interface that you can be sure that this class has all the properties and methods that are defined within the interface.

A variable of the type IDbConnection can hold a SqlConnection or a OracleClientConnection. You could only talk to Sql Express if you used a SqlConnection variable.

There's a better explanation of that idea over here[^].

Ahamed Azeem wrote:
Your second answer is not clear to me. Could you pls explain more

The first alternative usage is a namespace alias[^]. That would allow you to "rename" the namespace. This is common in Office-development to shorten the namespaces. As an example;

static class SomeClass 
{
  static void someMethod () 
  {
    System.Diagnostics.Debug.WriteLine("bla");
  }
}

With a namespace-alias, it would look like this;

using Diag = System.Diagnostics;
static class SomeClass 
{
  static void someMethod () 
  {
   Diag.Debug.WriteLine("bla");
  }
}

The second alternative[^] use is what the "interviewer" wanted to hear, and looks like this;

using (Font font1 = new Font("Arial", 10.0f)) 
{
    byte charset = font1.GdiCharSet;
}

This ensures that IDisposable is called cleaning up the Font.

Happy Reading Smile | :)

Ahamed Azeem1-Apr-10 6:22

1-Apr-10 6:22

Thanks a lot.. now i got it

Regards
Azeem

dan!sh 1-Apr-10 3:45

dan!sh

1-Apr-10 3:45

Ahamed Azeem wrote:
real time use of an interface

This is what I can think right away:

I am owner of an application. There are two distant and independent teams which are working on it. One on UI and other on rest of the layers. Now, as an owner, what I can do is provide both the teams with a interfaces so that they can work independently and be sure of what is the middle and DB layer is going to offer and what UI is supposed to consume.

There are plenty more uses of interfaces, one being dependency injection, which you might find through google. Smile | :)

Getting an article published on CodeProject should be easier and faster.

Luc Pattyn1-Apr-10 3:47

Luc Pattyn

1-Apr-10 3:47

Hi,

IMO you should buy and study a book on C# or change your career plans; those were very basic questions after all.

Hmmm | :|

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Eddy Vluggen1-Apr-10 5:48

1-Apr-10 5:48

Ahamed Azeem1-Apr-10 6:20

1-Apr-10 6:20

Dear Gentleman,

Is there any rule that basic question would not be answered..

I am very good fan of this forum.

Regards
Azeem

Dave Kreskowiak5-Apr-10 3:27

Dave Kreskowiak

5-Apr-10 3:27

That's not the problem.

The problem is that you were interviewing for a C# job without knowing the most basic concepts of C# and OOP programming.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

Ahamed Azeem5-Apr-10 4:22

5-Apr-10 4:22

Thank you

how to create MDI form in c#.net with menus

Abhinav S1-Apr-10 6:15

Abhinav S

1-Apr-10 6:15

Ahamed Azeem wrote:
for "Using"

Real time use of an interface - Late binding.

"Using" is often used to define a scope inside which an object will be garbage collected.

As suggested, you need to pick up a good C# book and read.

Me, I'm dishonest. And a dishonest man you can always trust to be dishonest.
Honestly. It's the honest ones you want to watch out for...

developerit21-Mar-10 0:24

developerit

21-Mar-10 0:24

how to create MDI form in c#.net with menus . can You Give me Example which helps me

Re: how to create MDI form in c#.net with menus

Abhinav S21-Mar-10 1:01

Abhinav S

21-Mar-10 1:01

See here[^].

Me, I'm dishonest. And a dishonest man you can always trust to be dishonest.
Honestly. It's the honest ones you want to watch out for...

Which tools is better to design the UI (user interface)?

yu-jian17-Mar-10 16:32

yu-jian

17-Mar-10 16:32

I am using the visio to design the UI, but I think that the effect is boring. Which tools are you using to design the software GUI? Big Grin | :-D

Re: Which tools is better to design the UI (user interface)?

Eddy Vluggen18-Mar-10 2:48

Re: Which tools is better to design the UI (user interface)?

18-Mar-10 2:48

yu-jian wrote:
I am using the visio to design the UI, but I think that the effect is boring.

That depends on what you're trying to design. Visio is used to quickly draw a screen, but it's not meant as a tool to create flashy forms - it's meant to show you where the buttons come, where the textboxes come - not how they are going to look like.

There's designers who can argue about the colors, the animations and the gradients. As a programmer, I only need to know what button where. Visio does that, and I agree that it's boring.

If you're creating an example to convince your client, then take a look at Photoshop; or XAML Smile | :)

I are Troll Suspicious | :suss:

dybs28-Mar-10 18:31

dybs

28-Mar-10 18:31

Why not just use the Visual Studio designer? If you're using Windows Forms (I assume this is the case since you posted in this forum), then you'll show exactly what the interface will look like. If you need to send an image to someone or use it in a presentation, just take a screenshot of the interface.

Dybs

The shout of progress is not "Eureka!" it's "Strange... that's not what i expected". - peterchen

Drag and move a button anywhere on the form

phani2548517-Mar-10 14:49

phani25485

17-Mar-10 14:49

Hi I want to develop a small app where i can position some controls like button, textbox, label etc and when i run the form I must be able to move the controls ie drag and drop anywhere on the form
could u refer me few articles with simple explanation, I am a beginner , thanks

yu-jian17-Mar-10 17:55

yu-jian

17-Mar-10 17:55

Add the event OnMouseDown of controls.
When OnMouseDown, get the current mouse position and set the new mouse position to the controls.
When OnMouseUp, donnot set the new mouse positon to the controls.

Som Shekhar17-Mar-10 20:51

Som Shekhar

17-Mar-10 20:51

A few changes from Yu-Jian.

1. create two variables
a)bool allowDrag
b)Point lastPosition

2. on Mouse Down, set allowDrag to true and set lastPosition of Mouse

3. on Mouse Up, set allowDrag to false

4. on Mouse Move, if allowDrag is true, change the location of the button based on the new location and previous location.

phani2548517-Mar-10 22:38

phani25485

17-Mar-10 22:38

Could u please provide the code, its confusing and i am new to windows programming

yu-jian18-Mar-10 15:52

yu-jian

18-Mar-10 15:52

Only one button in the form.

<br />
using System;<br />
using System.Collections.Generic;<br />
using System.ComponentModel;<br />
using System.Data;<br />
using System.Drawing;<br />
using System.Linq;<br />
using System.Text;<br />
using System.Windows.Forms;<br />
<br />
namespace WindowsFormsApplication5<br />
{<br />
    public partial class Form1 : Form<br />
    {<br />
        public Form1()<br />
        {<br />
            InitializeComponent();<br />
            this.button1.MouseMove += new MouseEventHandler(Form1_MouseMove);<br />
        }<br />
<br />
        private void button1_MouseDown(object sender, MouseEventArgs e)<br />
        {<br />
            this._allowDrag = true;<br />
        }<br />
<br />
        /// <summary><br />
        /// Recore the bool value; if true, the button's positon will be changed;<br />
        /// </summary><br />
        private bool _allowDrag;<br />
<br />
        private void Form1_MouseMove(object sender, MouseEventArgs e)<br />
        {<br />
            if (this._allowDrag)<br />
            {<br />
                this.button1.Location = new Point(e.X + this.button1.Location.X, e.Y + this.button1.Location.Y);<br />
            }<br />
        }<br />
<br />
        private void button1_MouseUp(object sender, MouseEventArgs e)<br />
        {<br />
            if (this._allowDrag)<br />
                this._allowDrag = false;<br />
        }<br />
    }<br />
}<br />
<br />