help with c# classes

Question

valter 0 Junior Poster in Training

14 Years Ago

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

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;
                }
        }

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

Edited 11 Years Ago by mike_2000_17 because: Fixed formatting

4 Contributors
13 Replies
485 Views
2 Weeks Discussion Span
Latest Post 14 Years Ago Latest Post by sknake

All 13 Replies

Ramy Mahrous 401 Postaholic

14 Years Ago

You just need to close the code tag.
You should have another property holding image file path

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...

Edited 11 Years Ago by pritaeas because: Fixed formatting.

Ramy Mahrous 401 Postaholic

14 Years Ago

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..

sknake commented: agreed +14

DdoubleD 315 Posting Shark

14 Years Ago

Here's the thing I am trying to load an arraylist of objects with each object having several text properties. Now if I try to do this with this modified code below, I can see each element of the arraylist but not the properties belonging to each object P. I have read many books over the past few weeks and rewritten the code a lot, but I just can't make this work.
Any takers please.
if (Parts.Length > 0)
                Title = GetTitle(parentName);
            ArrayList ps = new ArrayList();
            for (int counter = 0; counter < Parts.Length - 2; counter++)
            {
                PersonalPhoto P = new PersonalPhoto();
               // PhotoStuff P = new PhotoStuff();
                P.FileName = Parts[counter];
                P.DateTaken = GetDatePictureTaken(temp);
                P.Title = Title[counter];
                ps.Add(P);
            }

To access the items in your ArrayList ps, you need to cast the item back to type PersonalPhoto:

for (int i=0; i<ps.Count; i++)
{
  PersonalPhoto p = (PersonalPhoto)ps[i];
  // Now you can access the PersonalPhoto item's properties (eg. p.FileName)
  Console.WriteLine(p.FileName);
}

As an alternative, you could use a strong-typed List instead of an ArrayList:

List<PersonalPhoto> ps = new List<PersonalPhoto>();

            for (int counter = 0; counter < Parts.Length - 2; counter++)
            {
                PersonalPhoto P = new PersonalPhoto();
                // PhotoStuff P = new PhotoStuff();
                P.FileName = Parts[counter];
                P.DateTaken = GetDatePictureTaken(temp);
                P.Title = Title[counter];
                ps.Add(P);
            }

            // access each List/array element as PersonalPhoto...
            foreach (PersonalPhoto p in ps)
            {
                Console.WriteLine(p.FileName);
                Console.WriteLine(p.Title);
                // .... etc.
            }
            // or using index like:
            for (int i = 0; i < ps.Count; i++)
            {
                Console.WriteLine(ps[i].FileName);
                Console.WriteLine(ps[i].Title);
            }

Edited 14 Years Ago by DdoubleD because: n/a

valter commented: Very helpful, solved for what was for me a difficult problem +3

sknake 1,622 Senior Poster

14 Years Ago

Here is multiple examples of loading collections accessible by index.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;

namespace daniweb
{
  public class PhotoStuff
  {
    protected string _fileName;
    protected string _title;
    protected DateTime _date;

    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 virtual Image GetImage()
    {
      return Image.FromFile(this.FileName);
    }
    public PhotoStuff()
    {
    }
    public PhotoStuff(string FileName, string Title, DateTime Date)
      : this()
    {
      this.FileName = FileName;
      this.Title = Title;
      this.Date = Date;
    }
    public static PhotoStuff[] LoadFromSomething()
    {
      List<PhotoStuff> lst = new List<PhotoStuff>();
      lst.Add(new PhotoStuff(@"C:\img\iconError.png", "Error Icon", DateTime.Today));
      lst.Add(new PhotoStuff(@"C:\img\refresh_small.png", "Small Refresh Icon", DateTime.Today.AddDays(-1)));
      return lst.ToArray();
    }
  }
  public class PersonalPhoto : PhotoStuff
  {
    private string _photographer;
    public string Photographer
    {
      get { return _photographer; }
      set { _photographer = value; }
    }
    public PersonalPhoto()
      : base()
    {
    }
    public PersonalPhoto(string FileName, string Title, DateTime Date, string Photographer)
      : base(FileName, Title, Date)
    {
      this.Photographer = Photographer;
    }
    public static PersonalPhoto[] LoadFromSomething()
    {
      List<PersonalPhoto> lst = new List<PersonalPhoto>();
      lst.Add(new PersonalPhoto(@"C:\img\iconError.png", "Error Icon", DateTime.Today, "The computer"));
      lst.Add(new PersonalPhoto(@"C:\img\refresh_small.png", "Small Refresh Icon", DateTime.Today.AddDays(-1), "A camera"));
      return lst.ToArray();
    }
  }
}

Calling it:

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)
    {
      {
        //Single instance
        PersonalPhoto foto = new PersonalPhoto();
        foto.Date = DateTime.Now;
        foto.FileName = @"C:\something.jpg";
        foto.Photographer = "Me!!!";
      }
      {
        //Single instace
        PhotoStuff foto = new PhotoStuff();
        foto.Date = DateTime.Now;
        foto.FileName = @"C:\something.jpg";
      }
      {
        //Array and list, accessible by index
        PersonalPhoto[] personalPhotoArray = PersonalPhoto.LoadFromSomething();
        List<PersonalPhoto> personalPhotoList = PersonalPhoto.LoadFromSomething().ToList();

        Console.WriteLine(personalPhotoArray[0].FileName);
        Console.WriteLine(personalPhotoList[0].Title);
      }
      {
        //Array and list, accessible by index
        PhotoStuff[] personalPhotoArray = PhotoStuff.LoadFromSomething();
        List<PhotoStuff> personalPhotoList = PhotoStuff.LoadFromSomething().ToList();

        Console.WriteLine(personalPhotoArray[0].FileName);
        Console.WriteLine(personalPhotoList[0].Title);
      }
      {
        //Loading outside the class
        List<PhotoStuff> lst = new List<PhotoStuff>();
        for (int i1 = 0; i1 < 10; i1++)
        {
          string fName = string.Format(@"C:\test{0:F0}.bmp", i1);
          string title = Guid.NewGuid().ToString(); //test data
          DateTime photoDate = DateTime.Today.AddDays(-1 * i1);
          lst.Add(new PhotoStuff(fName, title, photoDate));
        }
      }
    }
  }
}

valter commented: member has been very helpful, and provided good examples to explain his point +3

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Very helpful, solved for what was for me a difficult problem
member has been very helpful, and provided good examples to explain his point

DdoubleD 315 Posting Shark · Answer 1 · 2009-09-17T20:20:40+00:00

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).

valter 0 Junior Poster in Training · Answer 2 · 2009-09-18T11:19:40+00:00

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.

sknake 1,622 Senior Poster Featured Poster · Answer 3 · 2009-09-18T11:36:42+00:00

1. Here is a mock photo class:

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:

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:

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:

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);
    }
  }
}

valter 0 Junior Poster in Training · Answer 4 · 2009-09-18T13:20:53+00:00

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.

sknake 1,622 Senior Poster Featured Poster · Answer 5 · 2009-09-18T13:23:10+00:00

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

if (foto.Photo.Count > 0)
        this.BackgroundImage = (foto.Photo[0] as Image);

Is that not what you wanted?

valter 0 Junior Poster in Training · Answer 6 · 2009-09-20T07:23:16+00:00

Thanks to all who responded I have been studying your answers.
sknake I cannot understand the code.

public PersonalPhoto()
: base()

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 0 Junior Poster in Training · Answer 7 · 2009-09-20T07:36:41+00:00

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

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.

sknake 1,622 Senior Poster Featured Poster · Answer 8 · 2009-09-20T16:44:22+00:00

It was using inheritince, and base() calls the base constructor.

public class PersonalPhoto : PhotoStuff
{
  public PersonalPhoto(): base()

In this case base() calls the ctor for PhotoStuff()

valter 0 Junior Poster in Training · Answer 9 · 2009-10-05T10:53:48+00:00

I am still wrestling with this class code. Using what sknake sent this is an excerpt from a method in the class.
Now this works fine eg ps[1]= a file name etc

if (Parts.Length > 0)
                Title = GetTitle(parentName);
            ArrayList ps = new ArrayList();
            for (int counter = 0; counter < Parts.Length - 2; counter++)
            {
                PersonalPhoto P = new PersonalPhoto();
               // PhotoStuff P = new PhotoStuff();
                P.FileName = Parts[counter];
                ps.Add(P.FileName);
                P.DateTaken = GetDatePictureTaken(temp);
                ps.Add(P.DateTaken);
                P.Title = Title[counter];
                ps.Add(P.Title);
            }

Here's the thing I am trying to load an arraylist of objects with each object having several text properties. Now if I try to do this with this modified code below, I can see each element of the arraylist but not the properties belonging to each object P. I have read many books over the past few weeks and rewritten the code a lot, but I just can't make this work.

Any takers please.

if (Parts.Length > 0)
                Title = GetTitle(parentName);
            ArrayList ps = new ArrayList();
            for (int counter = 0; counter < Parts.Length - 2; counter++)
            {
                PersonalPhoto P = new PersonalPhoto();
               // PhotoStuff P = new PhotoStuff();
                P.FileName = Parts[counter];
                P.DateTaken = GetDatePictureTaken(temp);
                P.Title = Title[counter];
                ps.Add(P);
            }

help with c# classes

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