System.Collection.IList

Question

not sure ive got a full grasp on this IList thing yet.. so something like : SavePerson() Person p = new p. ??

Vulpes · Answer

Can you post the code within the click handler for the button which the user presses to add a new salesman. If the code calls any methods post the code for those methods too.

ICE QUEEN · Answer

i checked the txt file and its empty too

ICE QUEEN · Answer

ok, this is where we are at, ERROR FREE! but i think its worse, because the code is running as i expected so where do i begin?. So i ran the application, chose to enter a new Salesman (after the user clicks enter the same form just stays there, i dont quite like that i tried a try catch statement with msg box prompts to move away but it mucked up my validation so i took it out.) then i went to the the form that's supposed to display all the names in the system and the listbox remained empty even though i entered 2 new records????

Vulpes · Answer

You have to specify a 'type argument' (the type between ) when creating an object of a generic type such as List . So the GetAllSalesman method should be defined and coded like this: private List GetAllSalesman() { List names = new List (); foreach(Salesman s in salesmanList) { names.Add(s.LastName + " " + s.FirstName); } return names; } If this method is or could be accessed from a different form, then replace 'private' with internal static. If 'NamesListed' is the class name of the form that it's in, you can call the method from the main form like this: private void aLLToolStripMenuItem_Click(object sender, EventArgs e) { List names = NamesListed.GetAllSalesman(); // do something with names }

ICE QUEEN · Answer

ok down to one error now, (fingers crossed!) the type or namespace name ListAllSalesman could not be found in Main. it comes from this method: private ListAllSalesman GetAllSalesman() { List names = new List (); foreach(Salesman s in salesmanList) { names.Add(s.LastName + " " + s.FirstName); } return names; }

ICE QUEEN · Answer

hopefully this is the last 2 errors, it is contained in Main private void aLLToolStripMenuItem_Click(object sender, EventArgs e) { s.ListAllSalesman(); } //Lists the names of all the Salesman recorded in the system private ListAllSalesman GetAllSalesman() { List names = new List (); foreach(Salesman s in salesmanList) { names.Add(s.LastName + " " + s.FirstName); } return names; }

Vulpes · Answer

Those last two errors are easily solved by adding this 'using' directive to the others at the top of the file: using System.IO; I'm surprised you don't have that one already.

ICE QUEEN · Answer

yup ive checked everything thrice now, looks exactly like urs, but i still have 16 Errors- it says File does not exist in the current context. The type or namespace name StreamReader could not be found...

Vulpes · Answer

Make sure the code is exactly like I posted earlier. There should be a semi-colon at the end of this line: string line; and the brackets in this line should be as follows: if(File.Exists(dataPath)) LoadSalesman();

ICE QUEEN · Answer

it says if(File.Exists(dataPath) LoadSalesman()); )expected BUT it doesnt selong there???

ICE QUEEN · Answer

and it says the same line while((line = sr.ReadLine ()) ! = null) is an invalid expression???

ICE QUEEN · Answer

it say expected ; for this line in main " while((line = sr.ReadLine ()) ! = null)"

Vulpes · Answer

You can put the methods wherever it's most useful to have them. All you have to remember is to declare them 'internal static' if they're going to be accessed from another form. You then just precede them with the name of the form, when you want to call them from some other form. What errors are you getting?

ICE QUEEN · Answer

private void Main_Load(object sender, EventArgs e) { if(File.Exists(dataPath) LoadSalesman()); } private void LoadSalesman() { using(StreamReader sr = new StreamReader(dataPath)) { string line; while((line = sr.ReadLine ()) ! = null) these lines are causing me 16 ERRORS????????? help!!!!!

ICE QUEEN · Answer

so what ure saying is that all the methods we've just created needs to be moved to Main(Parent Window)??? i have them in my first child form

Vulpes · Answer

If you need to access your List from a form other than the main form, then I'd change it's declaration to this: internal static List persons = new List (); Nothing else needs to be changed in the main form. You can now access the List from the other form with this syntax: Form1.persons (replace Form1 with the class name of the main form if different). Similarly, if you need to access any methods on the main form make them 'internal static' rather than 'private'. They can then be called like this: Form1.GetPersonNames();

ICE QUEEN · Answer

Here u are referring to the MAIN PARENT WINDOW right?

ICE QUEEN · Answer

Vulpes, I created a new form "Names Listed" with the listbox to display names in the system. It says:Error 4 The name 'persons' does not exist in the current context 'GetPersonNames() does not exist, hellllp!!!

Vulpes · Answer

You only need to load the contents of the file when the application first starts. After that the List is an in-memory representation of what's in the file and so you can operate directly on that. Incidentally, the code to load the file would be on these lines: private List persons = new List (); private void Form1_Load(object sender, EventArgs e) { if(File.Exists(dataPath) LoadPersons(); // don't need to do anything if file doesn't exist as StreamWriter will create it } private void LoadPersons() { using(StreamReader sr = new StreamReader(dataPath)) { string line; while((line = sr.ReadLine()) != null) { string[] items = line.Split('|'); Person p = new Person(items[0], items[1]); p.Country = items[3]; // etc persons.Add(p); } } } When I say make the appropriate changes to the List , I mean add a new element to it, remove an element from it or edit an existing element. All of these actions will, of course, be triggered by user input and should have their own method to do the necessary stuff. When developing an MDI application, it's not a good idea to add any controls to the parent other than a menu. So I'd stick with what you're already doing - particularly as you don't have time now to change it to something else.

ICE QUEEN · Answer

im thinking i can do one form with a group box do u know how this works with MDI?? the last one i tried the validation controls didnt work??

ICE QUEEN · Answer

when u say "start off by making the appropriate changes to the Person, u do mean user input right or are u referring to changes in the method itself?

ICE QUEEN · Answer

(as i understand it, but then again my brain is fried) wouldn't the "list all names in the system() method " require the info to be written from file? i think that's what is expected.

Vulpes · Answer

The SavePersons method should be on these lines: private void SavePersons() { using(StreamWriter sw = new StreamWriter(dataPath)) // need to overwrite existing file { foreach(Person p in persons) { string line = String.Format("{0}|{1}|{2}", p.FirstName, p.LastName, p.Country); sw.WriteLine(line); } } } Now in your 'create', 'edit' or 'replace' person methods, start off by making the appropriate changes to the List and then just call this method at the end: SavePersons();

System.Collection.IList

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Answers (23)