Would it be able to create a list with number ranging from 1 to 1000 and then assigning them to rows of a column of a data table

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Hi i created a list that creates number for me. The code to the list looks as follows

List<int> add_list = new List<int>();
    for (int i = 0; i < 400; i++)
    {
        add_list.Add(i);
    }

Next im taking each number and im assigning it to a sale order column in my DataTable Data table i created.

The problem im getting is when i close the app and open it again the list keeps starting from one and it shouldnt, it should start where it last stopped.

What I have tried:

I've tried to write every number in to a txt file on my desktop. It then reads the txt file and if the txt fil doesn't have the number in it starts from there.

Is there an easier way to do this then the way im doing it?

Posted 6-Sep-18 1:56am

Member 13475897

Updated 6-Sep-18 2:30am

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CHill60 6-Sep-18 8:01am

You need to store where you got up to somewhere ... how about a database? Most databases will actually do this for you with an "Identity Column".

The text file idea should work as well though ... or a config file ... or in the registry

Member 13475897 6-Sep-18 8:15am

so i just create a table and put in one column as the self incrementing identity column? I would then have to read down every number in the table and show it in my data table. How wil i only take number that have not been used before. for example i'm creating orders then i need to asign an unique order number to each order. if i just read all those numbers from sql to my list how wil i make sure im not using a duplicate. if there is about 1000 records in my table there wil be 1000 numbers so there wil be 1000 numbers in my list. How do i filter those numbers to not start from 1 again. Only way i see it possible is creating an action orders table and saving all the info in the table then with the self incrementing order number column i can read it into my datatable but i need to asign the number to an order before im saving it to sql sort of like an overview of what you purchased then they have the option(button) to save the sale to sql

CHill60 6-Sep-18 8:23am

If you are creating orders then surely you are storing those orders somewhere? If it is in a SQL database just keep an identity column on the orders table itself. You can create the order immediately and then either delete it or change a status if it is not proceeeded with. Or you only "assign" an order number if they confirm they are preceding ... you don't need an order number in order to preview the purchase

Member 13475897 6-Sep-18 8:19am

or do i just select all the number out of my table and select the last record, throw it in a variable and start the list from that variable?

Member 13475897 6-Sep-18 8:21am

If i do it with the variable way do i just create a new record in sql everytime they click the button where an order number is stored?

CHill60 6-Sep-18 8:23am

Absolutely don't do it this way - if there is more than one user of the database this method will break.

Member 13475897 6-Sep-18 8:30am

What im doing is im creating an automated order right, then i have a data table which i let them view it in a data grid view. Up to this part ive not stored the order what so ever in sql. I then want to let them be able to delete the row way before they store it in sql so i have code that deletes the row but it searches up a spesific column in my datatable which is the ordernumber column. They then have to type in the order number in a text box which i provide and then click the delete button and it wil delete the record out of my datatable. Up to this point ive not stored anything in sql. The problem im having now i that when that order is created that shows the item and pricing and everything is that it has to automatically asign an order number to each record for the cashier to be able to delete the record. then after they are happy i write all the values in the datatable to an order table in my sql Orders table

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Maciej Los · Accepted Answer · 2018-09-06T02:30:00

You're working on objects in memory... That's the reason you loose the data stored in a list or datatable.

There's few ways to store data...

1. Files:
- text file (*.txt),
- XML,
- etc.

2. A'ka database files
- MS Excel file,
- MS Access database,

3. Databases
- MS SQL Server,
- SQLite,
- Oracle,
- PostgreSQL,
- etc.

If you work on DataTable, you can simply save your data by using DataTable.WriteXml[^] method. Tobe able to read data from Xml, use DataTable.ReadXml[^] method.

Note, that DataTable has set of columns. When you set AutoIncrement[^] property for one of them, the number of order (OrderId) will be increased automatically.

Example:

C#

DataColumn col1 = new DataColumn("AutoNumber", typeof(int));
col1.AutoIncrement = true;
col1.AutoIncrementSeed = 1;
col1.AutoIncrementStep = 1;
DataColumn col2 = new DataColumn("Name", typeof(string));
DataColumn col3 = new DataColumn("Age", typeof(int));

// Add columns to a new DataTable.
DataTable dt = new DataTable("table");
dt.Columns.Add(col1);
dt.Columns.Add(col2);
dt.Columns.Add(col3);

dt.Rows.Add(new object[]{null, "Damian", 22});
dt.Rows.Add(new object[]{null, "Rose", 20});
dt.Rows.Add(new object[]{null, "Angelica", 19});
dt.Rows.Add(new object[]{null, "Romeo", 21});

string myxml = @"D:\students.xml";
dt.WriteXml(myxml);
dt.Rows.Clear(); //temporary remove data
dt.ReadXml(myxml);//load again

Result:

AutoNumber    Name        Age
1             Damian      22 
2             Rose        20 
3             Angelica    19 
4             Romeo       21

Good luck!

For further details, please, read these articles:
Save and restore your form size and location[^]
Where should I store my data?[^]