如何使用C＃从文本文件中删除一行 [英] How to remove a line from Text File using C#
问题描述
我的应用程序可以将用户添加到文本文件中，当我单击添加用户按钮时，会在我的文本文件中附加一行。但是，如果我想删除用户？这可以通过在textBox中编写用户名并单击删除用户按钮来完成，但我不知道用什么来删除textFile中的行。
例如，我存储用户名的textFile有：
My app is able to add "users" to a text file, when I click on "Add User" button, a line is appended to my text file. But if I want to remove an user? That would be accomplished by writing the username in a textBox and click on "Remove User" button, but I don't know what to use to remove the line from the textFile.
For example, my textFile that is storing usernames has:
User01<br />
User02<br />
ChrisCreateBoss<br />
ChrisHD22<br />
如果我想删除 ChrisHD22 ，我必须在我的textBox1中编写ChrisHD22，当单击删除按钮时，streamWriter将删除显示 ChrisHD22 的行并让其他行保持不变。 />
我目前正在使用它来检查文本文件中是否存在用户名：
And if I want to remove ChrisHD22, I have to write ChrisHD22 in my textBox1 and when Remove button is clicked, a streamWriter would remove the line that says ChrisHD22 and let the other lines untouched.
I'm currently using this to check if the username exists in the text file:
if(File.ReadLines(usersPath).Contains(usertxt2.Text))
{
// What can I write here?
}
如果我不清楚请告诉我。
先谢谢 - CCB
If I wasn't clear please let me know.
Thanks in Advance - CCB
推荐答案
循环在所有行上创建原始行的副本，在此处放弃匹配的行。在LINQ中有这样的东西（或者你也可以用一些嵌套的if来实现它作为foreach循环）：
Loop over all lines and create a copy of the original lines where you leave away the matching lines. Something like this in LINQ (or you may implement it as foreach loop too with some nested if):
string item = usertxt2.Text.Trim();
var lines = File.ReadAllLines(usersPath).Where(line => line.Trim() != item).ToArray();
File.WriteAllLines(usersPath, lines);
干杯
Andi
Cheers
Andi
使用System.Runtime.Serialization中的'DataContract和'DataMember属性，您可以轻松地序列化和反序列化类。这里显示的代码尽可能简单，以说明所涉及的技术。
开头：
1. Windows窗体项目：
a。一个TextBox，'textBox1
b。 ListBox，'listBox1
c。 4个按钮：'btnAdd，'btnDelete，'btnSave，'btnLoad
2.这个简单的类：
Using the 'DataContract and 'DataMember Attributes in System.Runtime.Serialization you can easily serialize and de-serialize a Class. The code shown here is as simple as possible, to illustrate the techniques involved.
Start with:
1. A Windows Forms Project with:
a. a TextBox, 'textBox1
b. ListBox, 'listBox1
c. 4 buttons: 'btnAdd, 'btnDelete, 'btnSave, 'btnLoad
2. This simple class:
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization;
using System.Windows.Forms;
namespace March8_SimpleDB
{
[DataContract]
public class Users
{
[DataMember]
public List<string> UserList { set; get; }
[DataMember]
public string FileLocation { set; get; }
private static DataContractSerializer theSerializer;
public Users()
{
UserList = new List<string>();
// default write location
FileLocation = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
FileLocation = Path.Combine(FileLocation, @"DefaultUsersFile.xml");
}
public void Add(string newUser)
{
UserList.Add(newUser);
}
public void Remove(string xUser)
{
UserList.Remove(xUser);
}
public bool Contains(string user)
{
return (UserList.Contains(user));
}
public static void Serialize(Users theUsers)
{
if(theSerializer == null) theSerializer = new DataContractSerializer(typeof(Users));
try
{
using (FileStream stream = new FileStream(theUsers.FileLocation, FileMode.Create))
{
theSerializer.WriteObject(stream, theUsers);
}
}
catch (Exception)
{
throw new InvalidDataContractException("Can't save file to: " + theUsers.FileLocation);
}
MessageBox.Show("file successfully saved");
}
public static Users DeSerialize(Users theUsers)
{
// lazy load
if (theSerializer == null) theSerializer = new DataContractSerializer(typeof(Users));
Users result = null;
using (FileStream stream = new FileStream(theUsers.FileLocation, FileMode.Open))
{
try
{
result = (Users) theSerializer.ReadObject(stream);
theUsers.UserList = result.UserList;
}
catch (Exception)
{
throw new InvalidDataContractException("Can't read file at: " + theUsers.FileLocation);
}
}
MessageBox.Show("file read successfully");
return result;
}
}
}</string></string>以下是在主窗体中序列化和反序列化此类的方法：
Here's how you would serialize and de-serialize this class in the "main Form:"
using System;
using System.Windows.Forms;
namespace March8_SimpleDB
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private Users TheUsers;
private void Form1_Load(object sender, EventArgs e)
{
TheUsers = new Users();
}
private void btnAdd_Click(object sender, EventArgs e)
{
string text = textBox1.Text;
// no valid entry ?
if (string.IsNullOrWhiteSpace(text)) return;
// already have this User name ?
if (TheUsers.Contains(text)) return;
TheUsers.Add(text);
listBox1.Items.Add(text);
}
private void btnDelete_Click(object sender, EventArgs e)
{
object selection = listBox1.SelectedItem;
// no selection ?
if (selection == null) return;
string text = selection.ToString();
TheUsers.Remove(text);
listBox1.Items.Remove(selection);
}
private void btnSave_Click(object sender, EventArgs e)
{
TheUsers.UserList.Clear();
foreach (var itm in listBox1.Items)
{
TheUsers.Add(itm.ToString());
}
Users.Serialize(TheUsers);
}
private void btnLoad_Click(object sender, EventArgs e)
{
Users.DeSerialize(TheUsers);
listBox1.Items.Clear();
foreach (string user in TheUsers.UserList)
{
listBox1.Items.Add(user);
}
}
}
}注意：
1.是的，你可以使用'DataContract /'DataMember来序列化继承自通用列表或字典的类，但为了做到这一点，需要解决方法，因为序列化程序将只编写字典中的LIst或KeyValue对中的Items ，并将忽略标有DataMember的任何其他字段/属性。
2.静态类成员将被Serilializer忽略。
3.您可以使用'DataContract序列化字段;我认为，由于许多原因，更好的做法是养成使用Properties而不是Fields的习惯。请记住，即将推出的C＃6.0将允许轻松实现属性的内联初始化。
评论，建议，欢迎。
Notes:
1. Yes, you can use 'DataContract/'DataMember to serialize a Class that inherits from a Generic List, or Dictionary, but in order to do that a work-around is required because the Serializer will write only the Items in the LIst or KeyValue Pairs in the Dictionary, and will ignore any other Fields/Properties marked with 'DataMember.
2. Static Class members will be ignored by the Serilializer.
3. You can serialize Fields with 'DataContract; I think it's better practice, for many reasons, to get in the habit of using Properties rather than Fields. Keep in mind that the upcoming C# 6.0 will allow easy in-line initialization of Properties.
Comments, suggestions, welcome.
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