How to update textfile without overwriting what's already inside?

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I need to save various customer details onto a textile, I am currently able to save customer information however when I add a new customers' details the previous information is overwritten.

What I have tried:

Dim Filenum As Integer = FreeFile()

FileOpen(Filenum, "Z:\Desktop\original.txt", OpenMode.Output)

PrintLine(Filenum, txtBoxFullName.Text & txtBoxFullAddress.Text & txtBoxDateOfBirth.Text & txtBoxEmailAddress.Text & txtBoxPostcode.Text & txtBoxPhoneNumber.Text & txtBoxItemDetails.Text & txtBoxRepairDescription.Text & txtBoxDateOfBirth.Text)

FileClose(Filenum)

MessageBox.Show("Customer/s has been successfully registered")

Posted 21-Dec-17 3:38am

faiqaa

Updated 17-Jan-18 1:59am

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[no name] 21-Dec-17 9:59am

I don't know VB, but after a quick Google search I think you can use FileOpen(1, "TextFile1.txt", OpenMode.Append)
BTW: Think about, how you would decodes your lines :-)

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OriginalGriff · Answer 1 · 2017-12-21T04:13:00

Don't open it for Output: that specifically deletes the file if it exists and opens a new one: use OpenMode.Append instead.

But ... I would suggest that rather than keeping the data in a flat file, use a "defined format" file such as CSV, XML, or JSON - the latter is trivial to support a list of customers and can serialize and deserialize the entire list of instances in a single line of code if you use NewtonSoft.JSON: you can add it to your project via the NuGet Package Manager (Tools ... NuGet Package Manager ... Package Manager Console):

PM> Install-Package Newtonsoft.Json

And then just one line of code does all the work:

C#

File.WriteAllText(path, JsonConvert.SerializeObject(MyCustomers));

And

C#

MyCustomers =  JsonConvert.DeserializeObject<List<Customer>>(File.ReadAllText(path));

Plus, you get a file format that is usable directly in many other applications.