Strongly typed collection without generics

Good Morning Sir/Madam

Let us say that I created a class…

public class Subject

{

private string _code;

private string _description;

public string Code

{

get { return _code; }

set { _code = value; }

}

public string Description

{

get { return _description; }

set { _description = value; }

} // end property

public Subject()

{

//empty default

} // end method

public Subject(string Code, string Description)

{

this.Code = Code;

this.Description = Description;

} // end method

public override string ToString()

{

return _code + " : " + _description;

} // end method

}

Then I want to create a strongly typed collection used to store Subject objects but then I don't want to store duplicate objects with the :

public void Add(Subject subjectObj)

Please help me out..

If you want to implement a strongly typed collection without using generics, then the best approach is to implement CollectionBase which does most of the work for you:

http://msdn.microsoft.com/en-us/library/7a03ybbb(v=vs.100).aspx

So, in this case, I'd use:

using System;

using System.Collections;

public class Subject

{

private string _code;

private string _description;

public string Code

{

get { return _code; }

set { _code = value; }

}

public string Description

{

get { return _description; }

set { _description = value; }

} // end property

public Subject()

{

//empty default

} // end method

public Subject(string Code, string Description)

{

this.Code = Code;

this.Description = Description;

} // end method

public override string ToString()

{

return _code + " : " + _description;

} // end method

}

public class SubjectCollection : CollectionBase

{

public Subject this[int index]

{

get

{

return (Subject) List[index];

}

set

{

List[index] = value;

}

public int Add(Subject value)

{

return List.Add(value);

}

public int IndexOf(Subject value)

{

return List.IndexOf(value);

}

public void Insert(int index, Subject value)

{

List.Insert(index, value);

}

public void Remove(Subject value)

{

List.Remove(value);

}

public bool Contains(Subject value)

{

// If value is not of type Subject, this will return false.

return List.Contains(value);

}

protected override void OnInsert(int index, Object value)

{

if (List.Contains((Subject)value))

throw new ArgumentException("Can't add or insert duplicate objects.", "value");

}

protected override void OnSet(int index, Object oldValue, Object newValue)

{

if (!Object.Equals(oldValue, newValue) && List.Contains((Subject)newValue))

throw new ArgumentException("Can't set elements to duplicate objects.", "value");

}

protected override void OnValidate(Object value )

{

if (value.GetType() != typeof(Subject))

throw new ArgumentException("value must be of type Subject.", "value");

}

class Test

{

static void Main()

{

SubjectCollection sc = new SubjectCollection();

Subject s1 = new Subject("M1", "Maths");

Subject s2 = new Subject("P1", "Physics");

sc.Add(s1);

sc.Add(s2);

foreach(Subject s in sc)

{

Console.WriteLine("Code = {0}, Subject = {1}", s.Code, s.Description);

}

sc[0] = s1; // OK, setting to same object

//sc.Add(s1);

//sc[1] = s1;

Console.ReadKey();

}

}

If you try to uncomment either of the lines in bold, then you will get a 'duplicate object' exception.

Incidentally, when you say duplicate object, I've taken it that you mean the same object and not just a different object which happens to have the same Code and Description properties.

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Vulpes13y ago
If you want to implement a strongly typed collection without using generics, then the best approach is to implement CollectionBase which does most of the work for you:

http://msdn.microsoft.com/en-us/library/7a03ybbb(v=vs.100).aspx

So, in this case, I'd use:

using System;
using System.Collections;

public class Subject
{
private string _code;
private string _description;

public string Code
{

get { return _code; }
set { _code = value; }
}

public string Description
{

get { return _description; }
set { _description = value; }
} // end property

public Subject()
{
//empty default
} // end method

public Subject(string Code, string Description)
{
this.Code = Code;
this.Description = Description;
} // end method

public override string ToString()
{
return _code + " : " + _description;
} // end method
}

public class SubjectCollection : CollectionBase
{

public Subject this[int index]
{
get
{
return (Subject) List[index];
}

set
{
List[index] = value;
}
}

public int Add(Subject value)
{
return List.Add(value);
}

public int IndexOf(Subject value)
{
return List.IndexOf(value);
}

public void Insert(int index, Subject value)
{
List.Insert(index, value);
}

public void Remove(Subject value)
{
List.Remove(value);
}

public bool Contains(Subject value)
{
// If value is not of type Subject, this will return false.
return List.Contains(value);
}

protected override void OnInsert(int index, Object value)
{
if (List.Contains((Subject)value))
throw new ArgumentException("Can't add or insert duplicate objects.", "value");
}

protected override void OnSet(int index, Object oldValue, Object newValue)
{
if (!Object.Equals(oldValue, newValue) && List.Contains((Subject)newValue))
throw new ArgumentException("Can't set elements to duplicate objects.", "value");
}

protected override void OnValidate(Object value )
{
if (value.GetType() != typeof(Subject))
throw new ArgumentException("value must be of type Subject.", "value");
}

}

class Test
{
static void Main()
{
SubjectCollection sc = new SubjectCollection();

Subject s1 = new Subject("M1", "Maths");
Subject s2 = new Subject("P1", "Physics");

sc.Add(s1);
sc.Add(s2);
foreach(Subject s in sc)
{
Console.WriteLine("Code = {0}, Subject = {1}", s.Code, s.Description);
}

sc[0] = s1; // OK, setting to same object
//sc.Add(s1);
//sc[1] = s1;
Console.ReadKey();
}
}

If you try to uncomment either of the lines in bold, then you will get a 'duplicate object' exception.

Incidentally, when you say duplicate object, I've taken it that you mean the same object and not just a different object which happens to have the same Code and Description properties.