Help regarding class in c#

  • Thread starter Thread starter trialproduct2004
  • Start date Start date
T

trialproduct2004

Hi all
i am having application in c#.
I want to create array of class object at runtime.
I don't want to set array bound at design time.
How to set array bound at runtime and how to access array element?
Can some one help me.
Thanks in advance.
 
Hello

// creating array
int arraySize = 5;
object[] objectsArray = new object[arraySize];

// instantiation of each element
objectsArray[0] = "Hello";
objectsArray[1] = 10;
objectsArray[2] = 40.0;
objectsArray[3] = 15.0f;
objectsArray[4] = new Random( );

// working with elements
foreach (object o in objectsArray)
{
System.Diagnostics.Debug.WriteLine("object type: " +
o.GetType().ToString());
if (o is string)
System.Diagnostics.Debug.WriteLine("Hey, it's string: \"" + o.ToString() +
"\"");
}
 
Hi all
i am having application in c#.
I want to create array of class object at runtime.
I don't want to set array bound at design time.
How to set array bound at runtime and how to access array element?
Can some one help me.
Thanks in advance.
Click to expand...

I will assume I understand your questions. If not, please give us more
information and repost.

To construct an array:

Type <varname> = new Type[<length>];

example:

Int32[] values = new Int32[10];
// values now has indices 0 through 9 (10 elements)

To construct an array that doesn't start at index 0, you need to use a
method of the Array object:

Int32[] values = (Int32[])Array.CreateInstance(typeof(Int32),
new Int32[] { 10 }, new Int32[] { 1 });
// values now has indices 1 through 10

To store a value into the array:

values[5] = 23;

to retrieve a value from the array, just use values[x] wherever you need
to read the value at index x:

Int32 someValue = values[9];

If you want to resize the array, if that's what your question is, then
you need to allocate a new array of the new, correct, size, then copy
the elements from the old array to the new and replace the reference in
the variable with the new array, something like this (using the first,
0-based, example as a start):

Int32[] values = new Int32[10];
....
// "resize" to 20 elements
Int32[] newValues = new Int32[20];
Array.Copy(values, newValues, values.Length);
values = newValues;

Also, note that arrays containing objects (like class instances,
strings, etc.) as opposed to value types (Int32, DateTime, Boolean,
etc.) are defaulted to null, which means there are no objects stored in
the array to begin with. This means that the following will crash with a
null-reference exception:

String[] names = new String[10];
Int32 len = names[0].Length; // crash here, names[0] = null

Hope this answers some of your questions.
 
Hi trialproduct2004,
if you want to have an array like structure where you don't want to
specify the bounds, you can use a System.Collections.ArrayList object. It
takes objects as input and returns objects, you just have to cast to your
desired type i.e.

string name = "mark";
Label tag = new Label();

ArrayList list = new Arraylist();
list.Add(name);
list.Add(tag);

string returnedName = (string)list[0];
Label returnedTag = (Label)list[1];


the Arraylist will grow as you keep adding more items. If you do not
specify an inital size it start with 16 elements, then once it needs more
space it will double in size to 32 then 64 etc to give you more space.

Hope that helps
Mark R Dawson
http://www.markdawson.org
 
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