我有一个保存在文本文件中的对象列表，可以显示在表单上。但是现在我需要一个按钮，它只显示基于属性的列表中的某些对象，在我的案例中。下面是我尝试使用的代码，但无法使其工作。
private void brandToolStripMenuItem_Click(object sender, EventArgs e)
{
List<Car> BrandSelect = new List<Car>(cars);
var SelectBrand = from c in BrandSelect
where c.Brand == textBox1.Text
select c;
DisplayCar();
}
下面是完整的代码，如果需要更多信息，感谢您的帮助。
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 Car_Manager
{
public partial class Form1 : Form
{
string currentfile;
Car c;
int curIndex = -1;
List<Car> cars = new List<Car>();
public Form1()
{
InitializeComponent();
c = new Car();
saveFileDialog1.CreatePrompt = true;
saveFileDialog1.OverwritePrompt = true;
saveFileDialog1.FileName = "myText";
saveFileDialog1.DefaultExt = "txt";
saveFileDialog1.Filter =
"Text files (*.txt)|*.txt|All files (*.*)|*.*";
}
public void clearForm()
{
txtBrand.Text = "";
txtModel.Text = "";
txtYear.Text = "";
txtPrice.Text = "";
txtNumMiles.Text = "";
txtInformation.Text = "";
radAutomatic.Checked = false;
radManual.Checked = false;
radConvertible.Checked = false;
radCoupe.Checked = false;
radEstate.Checked = false;
radHatchback.Checked = false;
radHPV.Checked = false;
radSaloon.Checked = false;
radSUV.Checked = false;
}
private void DisplayCar()
{
txtBrand.Text = c.Brand;
txtModel.Text = c.Model;
txtYear.Text = c.Year;
txtPrice.Text = c.Price;
txtNumMiles.Text = c.NumMiles;
DisplayBody();
DisplayGear();
string str = "";
for (int i = 0; i < c.Information.Count(); i++)
str += c.Information[i] + "\r\n";
txtInformation.Text = str;
}
private void FormToObject()
{
c.Brand = txtBrand.Text;
c.Model = txtModel.Text;
c.Year = txtYear.Text;
c.Price = txtPrice.Text;
c.NumMiles = txtNumMiles.Text;
BodyCheck();
GearCheck();
}
private void BodyCheck()
{
if (radHatchback.Checked == true)
{ c.Body = radHatchback.Text; }
else if (radHPV.Checked == true)
{ c.Body = radHPV.Text; }
else if (radSUV.Checked == true)
{ c.Body = radSUV.Text; }
else if (radSaloon.Checked == true)
{ c.Body = radSaloon.Text; }
else if (radConvertible.Checked == true)
{ c.Body = radConvertible.Text; }
else if (radCoupe.Checked == true)
{ c.Body = radCoupe.Text; }
else if (radEstate.Checked == true)
{ c.Body = radEstate.Text; }
}
private void DisplayBody()
{
if (c.Body == "Hatchback")
{ radHatchback.PerformClick(); }
else if (c.Body == "HPV")
{ radHPV.PerformClick(); }
else if (c.Body == "SUV")
{ radSUV.PerformClick(); }
else if (c.Body == "Convertible")
{ radConvertible.PerformClick(); }
else if (c.Body == "Saloon")
{ radSaloon.PerformClick(); }
else if (c.Body == "Coupe")
{ radSaloon.PerformClick(); }
else if (c.Body == "Estate")
{ radEstate.PerformClick(); }
}
private void GearCheck()
{
if (radAutomatic.Checked == true)
{ c.GearBox = radAutomatic.Text; }
else if (radManual.Checked == true)
{ c.GearBox = radManual.Text; }
}
private void DisplayGear()
{
if (c.GearBox == "Manual")
{ radManual.PerformClick(); }
else if (c.GearBox == "Automatic")
{ radAutomatic.PerformClick(); }
}
private void openToolStripMenuItem_Click(object sender, EventArgs e)
{
openFileDialog1.ShowDialog();
currentfile = openFileDialog1.FileName;
saveToolStripMenuItem.Enabled = true;
Stream s1 = openFileDialog1.OpenFile();
StreamReader reader = new StreamReader(s1);
while (reader.Peek() != -1)
{
string str = reader.ReadLine();
Car c = new Car();
c.ReadString(str);
cars.Add(c);
}
curIndex = 0;
c = cars[curIndex];
DisplayCar();
reader.Close();
}
private void saveAsToolStripMenuItem_Click(object sender, EventArgs e)
{
// Save everything in a dialog box
saveFileDialog1.ShowDialog();
// Open the file and save the information
Stream textOut = saveFileDialog1.OpenFile();
StreamWriter writer = new StreamWriter(textOut);
FormToObject();
string str = c.GetToString();
writer.WriteLine(str);
writer.Close();
}
private void saveToolStripMenuItem_Click(object sender, EventArgs e)
{
// Save the file with the current file name
FileStream f1 = new FileStream(currentfile, FileMode.Create, FileAccess.Write);
StreamWriter writer = new StreamWriter(f1);
// get the object into a string
FormToObject();
StreamWriter file = new System.IO.StreamWriter(f1);
cars.ForEach(file.WriteLine);
file.Close();
}
private void btnAddInfo_Click(object sender, EventArgs e)
{
c.Information.Add(txtAddInfo.Text);
string str = "";
for (int i = 0; i < c.Information.Count(); i++)
str += c.Information[i] + "\r\n";
txtInformation.Text = str;
}
private void exitToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Close();
}
private void btnClear_Click(object sender, EventArgs e)
{
txtInformation.Text = "";
}
private void addToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void btnPreviousCar_Click(object sender, EventArgs e)
{
curIndex--;
if (curIndex < 0)
curIndex = cars.Count - 1;
c = cars[curIndex];
DisplayCar();
}
private void btnNextCar_Click(object sender, EventArgs e)
{
curIndex++;
if (curIndex >= cars.Count)
curIndex = 0;
c = cars[curIndex];
DisplayCar();
}
private void button1_Click(object sender, EventArgs e)
{
int a = cars.Count;
textBox1.Text = Convert.ToString(cars[2]);
}
private void btnEditCar_Click(object sender, EventArgs e)
{
txtBrand.ReadOnly = false;
txtModel.ReadOnly = false;
txtYear.ReadOnly = false;
txtPrice.ReadOnly = false;
txtNumMiles.ReadOnly = false;
txtAddInfo.ReadOnly = false;
}
private void copyToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void brandToolStripMenuItem_Click(object sender, EventArgs e)
{
List<Car> BrandSelect = new List<Car>(cars);
var SelectBrand = from c in BrandSelect
where c.Brand == textBox1.Text
select c;
DisplayCar();
}
private void yearToolStripMenuItem1_Click(object sender, EventArgs e)
{
}
}
class Car
{
//List of properties
private string brand;
private string model;
private string year;
private string price;
private string numMiles;
private string body;
private string gearbox;
private List<string> information;
//Constructor
public Car() //Default Constructor
{
brand = "Unknown";
model = "Unknown";
year = "Unknown";
price = "Unknown";
numMiles = "Unknown";
information = new List<string>();
}
public Car(string str)
{
information = new List<string>();
ReadString(str);
}
public void ReadString(string str)
{
string[] words = str.Split('|');
int Nwords = words.Count();
brand = words[0];
model = words[1];
year = words[2];
price = words[3];
numMiles = words[4];
body = words[5];
gearbox = words[6];
information.Clear();
for (int i = 7; i < Nwords; i++)
information.Add(words[i]);
}
//Methods
public string Brand
{
get { return brand; }
set { brand = value; }
}
public string Model
{
get { return model; }
set { model = value; }
}
public string Year
{
get { return year; }
set { year = value; }
}
public string Price
{
get { return price; }
set { price = value; }
}
public string NumMiles
{
get { return numMiles; }
set { numMiles = value; }
}
public string Body
{
get { return body; }
set { body = value; }
}
public string GearBox
{
get { return gearbox; }
set { gearbox = value; }
}
public List<string> Information
{
get { return information; }
set { information = value; }
}
public string GetToString()
{
string str = "";
str += brand + "|";
str += model + "|";
str += year + "|";
str += price + "|";
str += numMiles + "|";
str += body + "|";
str += gearbox + "|";
for (int i = 0; i < information.Count(); i++)
str += information[i] + "|";
return str;
}
}
}
答案 0 :(得分：0)
我注意到的第一件事：
private void brandToolStripMenuItem_Click(object sender, EventArgs e)
{
// You already have list of cars, this line will copy your list
// into a new one, which is unnecessary work (you don't use it later).
// You don't need this:
List<Car> BrandSelect = new List<Car>(cars);
// the "c" here is not the "c" that is the field of your form
// it's a part of the syntax of linq query
var SelectBrand = from c in BrandSelect
where c.Brand == textBox1.Text
select c;
// This method displays what is in the field "c" (this.c)
// ... and the content of "c" didn't change at all
DisplayCar();
}
这里的代码应该是，例如：
private void brandToolStripMenuItem_Click(object sender, EventArgs e)
{
//beware this can be null
this.c = (from a in this.cars
where a.Brand == textBox1.Text
select a).FirstOrDefault();
}