如何在不覆盖已经存在的内容的情况下更新文本文件？
问题描述：
我需要将各种客户详细信息保存到纺织品上，我目前能够保存客户信息，但是当我添加新客户的详细信息时，之前的信息会被覆盖。
我的尝试：
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")
答
不要为输出打开它：如果文件存在并专门删除该文件并打开一个新文件：改为使用OpenMode.Append。
但是...我建议不要将数据保存在平面文件中，而是使用定义格式文件，例如CSV，XML或JSON - 后者很容易支持客户列表，并且可以序列化和反序列化整个如果您使用NewtonSoft.JSON，则只需一行代码中的实例列表：您可以通过NuGet包管理器（工具... NuGet包管理器...包管理器控制台）将其添加到您的项目中：
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然后只需要一行代码完成所有工作：
And then just one line of code does all the work:
File.WriteAllText(path, JsonConvert.SerializeObject(MyCustomers));和
And
MyCustomers = JsonConvert.DeserializeObject<List<Customer>>(File.ReadAllText(path));
另外，您可以获得可直接在许多其他应用程序中使用的文件格式。
Plus, you get a file format that is usable directly in many other applications.