用C#读写文本文件

Question

我正在编写一个程序,我需要从一个文本文件中读取,写入和过滤数据到新文件.
该计划的主要目标是:

• 让用户选择一个包含我已经创建的数据的文本文件,
• 使用Substring来选择从文件中抓取哪些字符,
• 编写一个与文本文件中的数据匹配的文件.

我有点坚持让程序一般写文件以及从文本文件中获取某些字符.
如果有人能给我一些很棒的指针.
谢谢!

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.Diagnostics;
using System.IO;

namespace Project_4_osmvoe
{
    public partial class Form1 : Form
    {
        string ham;
        StreamReader pizza;
        StreamWriter burger;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            DialogResult result = openFileDialog1.ShowDialog();
            if (result == DialogResult.OK)
            {
                ham = openFileDialog1.FileName;
            }
            pizza = new StreamReader(ham);
            lblInputFile.Text = ham;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            DialogResult result = saveFileDialog1.ShowDialog();
            if (result == DialogResult.OK)
            {
                ham = saveFileDialog1.FileName;
            }
            burger = new StreamWriter(ham);
            lblOutputFile.Text = ham;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            string line;
            while ((line = pizza.ReadLine()) != null)
            {
                if (filter(line))
                    burger.WriteLine(line);
            }
            pizza.Close();
            burger.Close();
            MessageBox.Show("Output File Written");
        }

        private Boolean filter(string intext)
        {
            string gender = intext.Substring(0, 0);
            string state = intext.Substring(0, 0);
            if (((radioButtonFemale.Checked && gender.Equals("F")) ||
                 (RadioButtonMale.Checked && gender.Equals("M"))))
                return true;
            else
                return false;
        }
    }
}

Answer 1

上述评论中收到的有用建议的一部分.
(不要在事件之间保持流打开)

您认为这些线的结果是什么？

    string gender = intext.Substring(0, 0);
    string state = intext.Substring(0, 0);

第二个参数Substring是从字符串中提取的字符数.传递零意味着返回的字符串为空,因此后续测试始终为false,您永远不会写一行.

我建议在两个不同的全局变量中存储两个文件的名称,并在button3_Click中打开两个流

string inputFile;
string outputFile;

private void button1_Click(object sender, EventArgs e)
{
    DialogResult result = openFileDialog1.ShowDialog();
    if (result == DialogResult.OK)
    {
        inputFile = openFileDialog1.FileName;
        lblInputFile.Text = inputFile;
    }
}

private void button2_Click(object sender, EventArgs e)
{
    DialogResult result = saveFileDialog1.ShowDialog();
    if (result == DialogResult.OK)
    {
        outputFile = saveFileDialog1.FileName;
        lblOutputFile.Text = outputFile ;
    }
}

private void button3_Click(object sender, EventArgs e)
{
    string line;
    using(StreamReader pizza = new StreamReader(inputFile))
    using(StreamWriter burger = new StreamWrite(outputFile))
    {
        while ((line = pizza.ReadLine()) != null)
        {
           if (!string.IsNullOrWhiteSpace(line) && filter(line))
               burger.WriteLine(line);
        }
    }
    MessageBox.Show("Output File Written");
}

private Boolean filter(string intext)
{
    string gender = intext.Substring(0, 1);
    string state = intext.Substring(0, 1);
    if (((radioButtonFemale.Checked && gender.Equals("F")) ||
         (RadioButtonMale.Checked && gender.Equals("M"))))
         return true;
    else
         return false;
}