Classes

Question

L.S. For my program I've to update a file. This can be done at two ways: 1. You load the last file and update it. 2. You start with a MT file and start from scratch. I want to do the last but my MT file consists of 50 category records which have to be loaded in the array. Because of the destructor I'm not able to do this within a Method. The data records will be destroyed and the end of the Method. How can I achieve this? ItemRec.cs namespace Stores { class ItemRec { public int index; public string descr; public double price; //Constructor public ItemRec(int c_index string c_descr double c_price) { index = c_index: descr = c_descr; price = c_price; } public int my_index { get {return index;} set {index = value;}} public string my_descr { get {return descrt;} set {descr = value;}} public double my_price {get {return price;} set {price = value;}} Program.cs List ItemRecN = new List (); Application.Run (new Form1()); Form1.cs public partial class Form1: Form { list ItemRecN = new (); ] public Form1() {} private void FileNew_Click(......................) { ItemRecN.Add(new Stores.ItemRec(0Stationary 0.00)); ItemRecN.Add(new Stores.Itemrec(1Books  0.00)); etc. etc. } Thanks and Regards Baily

theLizard · Answer

Take the declaration out of program.cs you do not need it there. Place the declaration before any forms constructor this will make it available in the scope of the form any method will be able to access it. Putting the declaration in a method makes it visible only to the method. using System; using System.Collections.Generic; using System.Text; using System.Drawing; namespace yourNameSpace { public class RecordItem { public int index; public string descr; public double price; public int Index { get{return(index);} set{index = value;} } } //-------------------------------------------------------------------------------------- public class RecordItems : List { public RecordItem AddItem { set{this.Add(value); } } //-------------------------------------------------------------------------------------- public RecordItems Index(int i) { return(this[i].index); } } } Create a class using the above example then all you have to do is this using yourNameSpace //before form constructors public RecordItem rec = new recordItem(); public RecordItems recItems = new RecordItems(); //declaring them public exposes them to ANY form that has access to the form so if you have say form1 and form2 you do not need to declare them in form 2 you can call them from form 2 with form1.rec = new RecordItem(); //form1.rec.index = 12345; etc... in your methods rec.desc = whatever rec.index = nextIndex; rec.price = 345.00; or in the class have a public void AddToList(RecordItems items int i string s double d) { items.Add(new recordItem()); items[items.Count-1].index = i; items[items.Count-1].desc = s; items[items.Count-1].price = d; } then to add to list recItems.AddItem(rec); or recItems.AddToList(recItems 1 Hello New Item 345.88); and thats it. to read through the list for(int i =0; i { targetvar = recItems[i].index; targetvar = recItems[i].desc; targetvar = recItems[i].price; } I still do not understand what you mean by MT records Do you want to create new ones each time or modify existing records for the tank?

Baily · Answer

Hi theLizard To answer your questions: Why in both programs? Without I get the following error: the name ItemRecN does not exist in the current file. What am I doing wrong? The List ..... has been declared in program.cs. Within program.cs form1.cs will be called and within form1.cs another form will be called for displaying the DataGridView. Can I make the following Method within the class? public void NewRecord() { ItemRecN.Add(new ItemRec(0 tank19.98)): ItemRecN.Add(new ItemRec(1tank28.54)): etc. etc. etc. } What I meant regarding the destructor is that according to my information the variables declared within a Method will be automatically deleted at the end of the Method by the destructor. I've tried to fill the array within a Method and it did not work. Please advise? The MT records is because a number of commodities are stored in tanks every tank has a identification code a maximum sounding value etc. These values are stored in the 50 MT records. Thanks and Regards Baily

theLizard · Answer

Why have you declared this List ItemRecN = new List (); in both program.cs and form1.cs If you start from an MT file how can you have 50 records to begin with? If you have a file with 50 records then you load an array with the 50 records and do what you need to do then delete the file and save a new one. What do you mean by this Because of the destructor I'm not able to do this within a Method. The data records will be destroyed and the end of the Method. And why have you started extra threads when these relate to your original ListBox question? You also need to decide on where your data is coming from and going to if its an sql type database then you don't really need to have a List ItemRecN = new List (); to load a grid it could be databound if that's the way you want to go otherwise a List allows you to manage your data from a binary file a lot easier. Finally there are a lot of learners on this forum some answer questions when they do not know what they are talking about just so their answer can be marked as ' accepted ' I have no need for my answers to be marked as accepted answers if you learn something from my answer that is good enough. Just remember in programming there are NO experts we ALL have something to learn from someone.