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Sep 17th, 2009

help with c# classes

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I am having a bit of trouble with a property.
I am developing a class "Photo" which has properties etc for a single photo

[code=c#]
using System.Drawing;

public Image Imge
{
get
{
try
{
return _Imge;
}
catch
{
Bitmap bm = new Bitmap(100, 100);
Graphics g = Graphics.FromImage(bm);
g.Clear(Color.WhiteSmoke);
Pen p = new Pen(Color.Red, 5);
g.DrawLine(p, 0, 0, 100, 100);
g.DrawLine(p, 100, 0, 0, 100);
return bm;
}
}
set {
using (Image _Imge = Image.FromFile(_FileName))
Imge = value;
}
}
[code]
I am trying to write a property that converts a filename to an image.
The problem is the last set statement gives a Cannot implicitly convert type error.

Thanks for any help

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valter

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Sep 17th, 2009

Re: help with c# classes

You just need to close the code tag by $[/code]$ not $[code]$ .
You should have another property holding image file path

C# Syntax (Toggle Plain Text)
public string ImageFilePath
{
get...
set....
}
public Image Imge
{
get
{
try
{
return _Imge;
}
catch
{
Bitmap bm = new Bitmap(100, 100);
Graphics g = Graphics.FromImage(bm);
g.Clear(Color.WhiteSmoke);
Pen p = new Pen(Color.Red, 5);
g.DrawLine(p, 0, 0, 100, 100);
g.DrawLine(p, 100, 0, 0, 100);
return bm;
}
}
set {
using (Image _Imge = Image.FromFile(ImageFilePath))
Imge = value;
}
}
public string ImageFilePath
{
get...
set....
}
public Image Imge
{
get
{
try
{
return _Imge;
}
catch
{
Bitmap bm = new Bitmap(100, 100);
Graphics g = Graphics.FromImage(bm);
g.Clear(Color.WhiteSmoke);
Pen p = new Pen(Color.Red, 5);
g.DrawLine(p, 0, 0, 100, 100);
g.DrawLine(p, 100, 0, 0, 100);
return bm;
}
}
set {
using (Image _Imge = Image.FromFile(ImageFilePath))
Imge = value;
}
}

Set the ImageFilePath first...

Ramy Mahrous

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Sep 17th, 2009

Re: help with c# classes

In your set statement, you create a new var of name "_Imge"--was that intended? And, you also call the property setter again with Imge = value --was that intended?

Maybe I've missed something, but I don't understand why you would return _Imge in your getter, but then call the setter again inside the set property, or why you would create, or attempt, what appears to be another instance for _Imge in the setter (and then not even use it).

Last edited by DdoubleD; Sep 17th, 2009 at 11:23 am. Reason: added end to last sentence

DdoubleD

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Posting Shark

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Sep 18th, 2009

Re: help with c# classes

Thanks for assistance with previous question.

I have two further short class questions.

1.
I have a class called photo which has 3 properties, filename, title, date, and a subclass called pack, which is an ArrayList of the photo objects, with it's own properties and methods.

My question is how do I access the photo properties once the object is in the ArrayList pack?

2. I wish to use other classes with the same project but I am confused with the inheritance issues.
I am not sure how many classes I can create.

I have read a great mass of information, including several books on c#, I know it is my deficiency, but does anyone have a site that might simplify it for me.

Thanks for any replies.

valter

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Sep 18th, 2009

Re: help with c# classes

1. Here is a mock photo class:

C# Syntax (Toggle Plain Text)
using System;
using System.Collections;
 
namespace daniweb
{
  public class PhotoStuff
  {
    private string _fileName;
    private string _title;
    private DateTime _date;
    private ArrayList _photo;
 
    public string FileName
    {
      get { return _fileName; }
      set { _fileName = value; }
    }
    public string Title
    {
      get { return _title; }
      set { _title = value; }
    }
    public DateTime Date
    {
      get { return _date; }
      set { _date = value; }
    }
    public ArrayList Photo
    {
      get { return _photo; }
      set { _photo = value; }
    }
 
    public PhotoStuff()
    {
      _photo = new ArrayList();
    }
  }
}
using System;
using System.Collections;

namespace daniweb
{
  public class PhotoStuff
  {
    private string _fileName;
    private string _title;
    private DateTime _date;
    private ArrayList _photo;

    public string FileName
    {
      get { return _fileName; }
      set { _fileName = value; }
    }
    public string Title
    {
      get { return _title; }
      set { _title = value; }
    }
    public DateTime Date
    {
      get { return _date; }
      set { _date = value; }
    }
    public ArrayList Photo
    {
      get { return _photo; }
      set { _photo = value; }
    }

    public PhotoStuff()
    {
      _photo = new ArrayList();
    }
  }
}

Inhering from the class and adding a "Photographer" string property to indicate who took the picture:

C# Syntax (Toggle Plain Text)
  public class PersonalPhoto : PhotoStuff
  {
    private string _photographer;
    public string Photographer
    {
      get { return _photographer; }
      set { _photographer = value; }
    }
 
    public PersonalPhoto()
      : base()
    {
    }
  }
  public class PersonalPhoto : PhotoStuff
  {
    private string _photographer;
    public string Photographer
    {
      get { return _photographer; }
      set { _photographer = value; }
    }

    public PersonalPhoto()
      : base()
    {
    }
  }

So altogether we have a single file with this:

C# Syntax (Toggle Plain Text)
using System;
using System.Collections;
 
namespace daniweb
{
  public class PhotoStuff
  {
    private string _fileName;
    private string _title;
    private DateTime _date;
    private ArrayList _photo;
 
    public string FileName
    {
      get { return _fileName; }
      set { _fileName = value; }
    }
    public string Title
    {
      get { return _title; }
      set { _title = value; }
    }
    public DateTime Date
    {
      get { return _date; }
      set { _date = value; }
    }
    public ArrayList Photo
    {
      get { return _photo; }
      set { _photo = value; }
    }
 
    public PhotoStuff()
    {
      _photo = new ArrayList();
    }
  }
  public class PersonalPhoto : PhotoStuff
  {
    private string _photographer;
    public string Photographer
    {
      get { return _photographer; }
      set { _photographer = value; }
    }
 
    public PersonalPhoto()
      : base()
    {
    }
  }
}
using System;
using System.Collections;

namespace daniweb
{
  public class PhotoStuff
  {
    private string _fileName;
    private string _title;
    private DateTime _date;
    private ArrayList _photo;

    public string FileName
    {
      get { return _fileName; }
      set { _fileName = value; }
    }
    public string Title
    {
      get { return _title; }
      set { _title = value; }
    }
    public DateTime Date
    {
      get { return _date; }
      set { _date = value; }
    }
    public ArrayList Photo
    {
      get { return _photo; }
      set { _photo = value; }
    }

    public PhotoStuff()
    {
      _photo = new ArrayList();
    }
  }
  public class PersonalPhoto : PhotoStuff
  {
    private string _photographer;
    public string Photographer
    {
      get { return _photographer; }
      set { _photographer = value; }
    }

    public PersonalPhoto()
      : base()
    {
    }
  }
}

And calling it:

C# Syntax (Toggle Plain Text)
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace daniweb
{
  public partial class PhotoStuffCaller : Form
  {
    public PhotoStuffCaller()
    {
      InitializeComponent();
    }
 
    private void button1_Click(object sender, EventArgs e)
    {
      PersonalPhoto foto = new PersonalPhoto();
      foto.Date = DateTime.Now;
      foto.FileName = @"C:\something.jpg";
      foto.Photographer = "Me!!!";
      if (foto.Photo.Count > 0)
        this.BackgroundImage = (foto.Photo[0] as Image);
    }
  }
}
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace daniweb
{
  public partial class PhotoStuffCaller : Form
  {
    public PhotoStuffCaller()
    {
      InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
      PersonalPhoto foto = new PersonalPhoto();
      foto.Date = DateTime.Now;
      foto.FileName = @"C:\something.jpg";
      foto.Photographer = "Me!!!";
      if (foto.Photo.Count > 0)
        this.BackgroundImage = (foto.Photo[0] as Image);
    }
  }
}

sknake

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Sep 18th, 2009

Re: help with c# classes

Thanks sknake,
I can follow that, what I don't quite get is how do I add a photo with its properties to the arraylist, to store say some 10 photos, and how I access a particular index.

valter

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Sep 18th, 2009

Re: help with c# classes

In the class I exposed the array list and accessed it by index:

C# Syntax (Toggle Plain Text)
      if (foto.Photo.Count > 0)
        this.BackgroundImage = (foto.Photo[0] as Image);
      if (foto.Photo.Count > 0)
        this.BackgroundImage = (foto.Photo[0] as Image);

Is that not what you wanted?

Last edited by sknake; Sep 18th, 2009 at 4:23 am.

sknake

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Sep 18th, 2009

Re: help with c# classes

Why ArrayList?! Are you fond of casting??
Use generics List<Photo> photos = new List<Photo>(); and in Photo class you may have list of photos and indexer to get them by index or name anything is unique..

Ramy Mahrous

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Sep 19th, 2009

Re: help with c# classes

Thanks to all who responded I have been studying your answers.
sknake I cannot understand the code.
[c#] #
public PersonalPhoto()
#
: base()
[/code]

What is this base?

Ramy,
I am trying to use ArrayList because I want to use a collection and this one is the only one I ( thought I understood).
I am trying to populate the array within the class, I notice you do this outside it. Also how would you call a method to set a property.

valter

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Sep 19th, 2009

Re: help with c# classes

Please disregard previous message, I messed up with the code delimiters, and I only sent a partial message.
I will try again.

sknake I cannot understand part of your code in the PersonalPhoto class

c# Syntax (Toggle Plain Text)
public PersonalPhoto()
: base()
public PersonalPhoto()
: base()

Also I note that you populate your ArrayList outside the class, I have been trying to do it inside the class after loading a file, is this not appropriate?
How do you call a method in your calling routine?

I use an ArrayList because I wanted to use a collection, and
an ArrayList is the most familiar to me.

valter

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