C#•2y ago

❔ Filling a combo box in a class that is from a form

So I have a project that requires me to use databases, I chose to use access database since I am familiar with it. But i am trying to put in some combo boxes with the data from the database. When I did that it worked, but my teacher asked me to put it in the same class that I read my data from. Is this possible?

29 Replies

AdmiraalSambaOP•2y ago

so this is the code I used to get the data from the database into the combo box and my teacher asked to do it in clsData (the class i am using to read data from the database to then use for things like my login page)

Omnissiah•2y ago

that would be a good idea one more layer could be even a better idea

AdmiraalSambaOP•2y ago

what do you mean with one more layer?

Omnissiah•2y ago

just start with ui and repository, then we'll see if other improvements are required

AdmiraalSambaOP•2y ago

being honest i don't really understand what you mean. Do you mean like improving the ui?

Omnissiah•2y ago

so, ui would be you form and controls repository would be the class that reads and writes data from the table this makes sense?

AdmiraalSambaOP•2y ago

yes, make the form and controls then the class and then improve them both

Omnissiah•2y ago

you will also need another class for the data returned by the repository you could think of making some folders in your solution

AdmiraalSambaOP•2y ago

Being honest never made a folder before in my solution

Omnissiah•2y ago

if you have like 1 or 2 files who cares, but when you start having a bunch of files that works on different stuff one from another you could start thinking about it

AdmiraalSambaOP•2y ago

oh oke 👍 So i made a folder with all my classes, but i dont know if i could do it better. So i have a class that does the calculations of how much insuline the user must use (program is for people with diabetes) and then i have a class for getting the things out of the database and then i have a class that contains all the info so it can be used globally So all of my forms are connected to the clsData (database class) and one of them is connected to clsBerekeningen (aka the class that does the calculations) and i also wanted to add a query that updates the product from the access database and the code does not work

public void EditProduct(clsGegevens geg)
        {

            string queryString = "UPDATE tblProduct SET " +
                            geg.Productnaam + " = @productNaam, " +
                            geg.Bereiding + " = @bereiding, " +
                            geg.Eenheid + " = @eenheid, "+
                            geg.AantalKoolhydraten + " = @aantalKoolhydraten, "+
                            geg.AantalCalorieen + " = @aantalCalorieen, "+
                            geg.Favorieten + " = @favoriet" +
                            "WHERE" + geg.Productnaam + " = @productNaam";

            using (OleDbConnection con = new OleDbConnection(_strConnect))
            {
                con.Open();
                using (OleDbCommand command = new OleDbCommand(queryString, con))
                {
                    command.Parameters.AddWithValue("@productNaam", geg.Productnaam);
                    command.Parameters.AddWithValue("@bereiding", geg.Bereiding);
                    command.Parameters.AddWithValue("@eenheid", geg.Eenheid);
                    command.Parameters.AddWithValue("@aantalKoolhydraten", geg.AantalKoolhydraten);
                    command.Parameters.AddWithValue("@aantalCalorieen", geg.AantalCalorieen);
                    command.Parameters.AddWithValue("@favoriet", geg.Favorieten);

                    command.ExecuteNonQuery();
                }
            }
        }

public void EditProduct(clsGegevens geg)
        {

            string queryString = "UPDATE tblProduct SET " +
                            geg.Productnaam + " = @productNaam, " +
                            geg.Bereiding + " = @bereiding, " +
                            geg.Eenheid + " = @eenheid, "+
                            geg.AantalKoolhydraten + " = @aantalKoolhydraten, "+
                            geg.AantalCalorieen + " = @aantalCalorieen, "+
                            geg.Favorieten + " = @favoriet" +
                            "WHERE" + geg.Productnaam + " = @productNaam";

            using (OleDbConnection con = new OleDbConnection(_strConnect))
            {
                con.Open();
                using (OleDbCommand command = new OleDbCommand(queryString, con))
                {
                    command.Parameters.AddWithValue("@productNaam", geg.Productnaam);
                    command.Parameters.AddWithValue("@bereiding", geg.Bereiding);
                    command.Parameters.AddWithValue("@eenheid", geg.Eenheid);
                    command.Parameters.AddWithValue("@aantalKoolhydraten", geg.AantalKoolhydraten);
                    command.Parameters.AddWithValue("@aantalCalorieen", geg.AantalCalorieen);
                    command.Parameters.AddWithValue("@favoriet", geg.Favorieten);

                    command.ExecuteNonQuery();
                }
            }
        }

that's the code i use to update the data geg. is the information class i use to get global variables

Omnissiah•2y ago

do you have a naming convention? if clsData deals with tblProduct, probably it could named ProductTable or ProductRepository same goes for clsBerekeningen, to know what it is at first sight, it could be for example InsulineCalculator or something does not work means that nothing happens? well for example this is wrong "WHERE" + geg.Productnaam + " = @productNaam"; first because there is no space after WHERE then because geg.Productnaam is the value, not the field name? and the same is for all other fields, you shouldn't be using geg into the query if you are passing it in the command.Parameters so it would be something like

string sql = @"UPDATE tblProduct SET
Productnaam = @productNaam,
Bereiding = @bereiding,
Eenheid = @eenheid,
AantalKoolhydraten = @aantalKoolhydraten,
AantalCalorieen = @aantalCalorieen,
Favorieten = @favoriet
WHERE Productnaam = @productNaam";

string sql = @"UPDATE tblProduct SET
Productnaam = @productNaam,
Bereiding = @bereiding,
Eenheid = @eenheid,
AantalKoolhydraten = @aantalKoolhydraten,
AantalCalorieen = @aantalCalorieen,
Favorieten = @favoriet
WHERE Productnaam = @productNaam";

i don't know the fields names but kind of like this also, is there not a ProductId, instead of searching for name?

AdmiraalSambaOP•2y ago

Its both things so i got tblProducts and tblLogin both coming from clsDate clsData* There is

Omnissiah•2y ago

i bet they are used in entirely different places, one is for authentication and one is the products, so maybe they could be splitted in two diffrent classes

AdmiraalSambaOP•2y ago

they are used in different places indeed, just in one form they both used (for the main form where i will have a tabcontrol with the products etc where they can select, edet products but also see their profile) the clsBerekeningen is used for multiple calculations and its a requirement to have a class this was my first thought on putting something in a class for the combo box?

Omnissiah•2y ago

yes but also in general, for using stuff that you get/put int a table by requirement you mean having one class with all the methods to calculate stuff in it?

AdmiraalSambaOP•2y ago

sort of yes, so our main requirements where have a extern database for full points, intern would be -15 points, a text file would be -25 points no database is 0 points we needed atleast one class

Omnissiah•2y ago

so you can have more classes

AdmiraalSambaOP•2y ago

Yes Just minimum 1 if we don't have any then 0 points on that

Omnissiah•2y ago

the practice is to organize code that works on the same stuff in a class or eventually same namespace

AdmiraalSambaOP•2y ago

Oke 🙂 My teacher told me also that i needed to do some stuff on the naming labels and stuff like making code efficient

Omnissiah•2y ago

that would be a good thing to do the basis of it is essentially how do you explain your intentions in your code

AdmiraalSambaOP•2y ago

So what it does?

Omnissiah•2y ago

what it does in the sense of what it does in the application

AdmiraalSambaOP•2y ago

Ooo hey dont, i got a file with all the requierments of what the projects needs to have.

Omnissiah•2y ago

and what about it

AdmiraalSambaOP•2y ago

If you want i can send them 🙂

Omnissiah•2y ago

wouldn't it be better if they were available here for everyone?

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Filling a combo box in a class that is from a form