如何在C＃中读取和删除文本？ [英] How do I read and delete from text in C#?

问题描述

我已经阅读了我的编程书，并看到了在线示例，尽管如此，我似乎无法让它工作。我可以从列表框中删除，但它不会从实际的txt文件中删除它。此外，它根本不会读。



我尝试过：

I've read my programming book, and seen online examples, nonetheless, I can not seem to get it to work. I can delete from the list box fine, but it will not delete it from the actual txt file. Furthermore, it will not read at all.

What I have tried:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;

namespace TripCostCalculator
{
    public partial class Form1 : Form
    {
        private const string dir = @"C:\C# 2015\Files\";
        private const string path = dir + "PayCheckCalculator.txt";
        decimal tax = .06m;
        
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            StreamReader textIn =
             new StreamReader(
             new FileStream(path, FileMode.OpenOrCreate, FileAccess.Read));
            textIn.Close();
        }
        private void btnCalculate_Click(object sender, EventArgs e)
        {
            string name = txtName.Text;
            decimal dph;
            decimal grossIncome;
            decimal netIncome;

            if (!decimal.TryParse(txtDph.Text, out dph))
            {
                MessageBox.Show("Please enter a valid dollar amount");
                return;
            }
            decimal hoursWorked;
            if (!decimal.TryParse(txtHoursWorked.Text, out hoursWorked))
            {
                MessageBox.Show("Please enter a valid dollar amount");
                return;
            }
            grossIncome = dph * hoursWorked;
            txtGrossIncome.Text = grossIncome.ToString("c");
            netIncome = grossIncome - (grossIncome * tax);
            txtNetIncome.Text = netIncome.ToString("c");

           
        }

        private void btnDelete_Click(object sender, EventArgs e)
        {
            for (int v = 0; v < lstSalary.SelectedItems.Count; v++)
            {
                lstSalary.Items.Remove(lstSalary.SelectedItems[v]);
            }
            if (System.IO.File.Exists(@"C:\C# 2015\Files\"))
            {
                System.IO.File.Delete("PayCheckCalculator.txt");
            }
           
        }

      
        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {

            lstSalary.Items.Add(txtName.Text);
            lstSalary.Items.Add(txtDph.Text);
            lstSalary.Items.Add(txtHoursWorked.Text);
            lstSalary.Items.Add(txtGrossIncome.Text);
            lstSalary.Items.Add(txtNetIncome.Text);

        }

        private void btnSave_Click_1(object sender, EventArgs e)
        {
            StreamWriter textOut = new StreamWriter(
             new FileStream(path, FileMode.OpenOrCreate | FileMode.Append, FileAccess.Write));



            textOut.Write(txtName.Text + ",");
            textOut.Write(txtDph.Text + ",");
            textOut.Write(txtHoursWorked.Text + ",");
            textOut.Write(txtGrossIncome + ",");
            textOut.Write(txtNetIncome.Text + ",");

            textOut.Close();

            txtName.Clear();
            txtDph.Clear();
            txtHoursWorked.Clear();
            txtGrossIncome.Clear();
            txtNetIncome.Clear();
        
    }

        
    }
   
}

推荐答案

附加到文本文件很容易;通过删除任意部分来更新文件将是一团糟。这就是数据库的用途，或者使用序列化/反序列化。



虽然有些人试图使文本文件成为一种随机访问数据库，imho，那是浪费时间，它还要求您处理文本编码，行尾字符的问题，并且文本文件的每个虚拟记录部分具有相同的长度或系统地用开始/结束分隔符括起来。请不要去那里！



在Form.Load事件中发生了什么，你创建一个新的StreamReader，打开和关闭一个文件，但是你做了没有读取文件，或者保持对Stream的引用？如果这只是为了确保文件存在，那么为什么不先检查它是否存在？

Appending to a text file is easy; updating the file by deleting arbitrary sections is going to be a mess. That's what databases are for, or using serialization/deserialization is for.

While some folks attempt to make a text file a kind of random-access database, imho, that's a waste of time, and it also requires that you deal with issues of text-encoding, line-end characters, and that each "virtual record" section of the text file have identical length or be bracketed systematically with start/end delimiters. Please, don't go there !

What's going on in the Form.Load event where you create a new StreamReader, and open and close a file, but you do not read the file, or, keep a reference to the Stream ? If that's just to make sure the file exists, then why not check if it exists first ?

private void Form1_Load(object sender, EventArgs e)
{
    if (! File.Exists(path))
    {
        using (FileStream fs = File.Create(path)){}
    }
}

你的代码没有读取，因为......好吧......你没有调用任何代码......我可以看到......读取文件？



想一想：



a。使用数据库，加上绑定到它的一些适当的UI控件（DataGridView？）



......或者......



b.1使用类EmployeePayRecord为员工记录建模



b.2创建EmployeePayRecord实例的集合等级。



c。使用非常方便和强大的WCF序列化工具，根据需要将集合保存到文件中，或者重新读取。



如果你真的不想使用一个数据库，看看这篇文章使用XML作为一个简单的数据存储与通常的CRUD工具：[ ^ ]。

Your code is not reading because ... well ... you are not calling any code ... that I can see ... to read the file ?

Think about:

a. use a database, coupled with some appropriate UI control bound to it (DataGridView ?)

... or ...

b.1 model the employee "record" with a Class, "EmployeePayRecord"

b.2 create a collection of instances of the "EmployeePayRecord" Class.

c. use the very convenient and powerful WCF serialization tools to save the collection to a file as needed, or read it back in.

If you really don't want to use a database, check out this article that uses XML as a simple "data store" with the usual CRUD facilities: [^].

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