C# LINQ

作者：貓貓風 ฅ●ω●ฅ│2017-06-25 22:36:43│巴幣：28│人氣：633

LINQ 個人認為是一個很方便的功能，可以把複雜的判斷式用簡單的描述即可達成相同效果

如果了解SQL語法就會覺得基本上是一樣的東西，結構上雷同(Select From Where)

只是陳述的順序有點不同，以下直接看範例了解比較快

此範例會隨機產生10個成員的集合，每個成員分別有編號、名稱、職業

然後當按下Query時，會按三種不同條件組合分別呈現從集合中查詢的結果

Source Code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace LINQTest
{
public partial class Form1 : Form
{
List<group> _group = new List<group>();
private string[] _name = new string[]
"Abigail","Adela","Alexia","Bblythe","Camille","Cornelia",
"Darlene","Edith","Erica","Eve"};
private string[] _member_class = new string[] { "magician", "warrior", "Knight" };
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
generate_dropdownList();
generate_member();
}
private void generate_dropdownList()
{
for (int i = 0; i <= _name.Length - 1; i++)
{
this.comboBox1.Items.Add(new combobox(_name[i], _name[i]));
}
this.comboBox1.SelectedIndex = 0;
for (int i = 1; i <= _name.Length; i++)
{
this.comboBox2.Items.Add(new combobox(i.ToString(), i.ToString()));
}
this.comboBox2.SelectedIndex = 0;
for (int i = 0; i <= _member_class.Length - 1; i++)
{
this.comboBox3.Items.Add(new combobox(_member_class[i],
_member_class[i]));
}
this.comboBox3.SelectedIndex = 0;
}
private void generate_member()
{
Random r = new Random();
for(int i = 1; i<= 10 ; i++)
{
group member = new group(); //建立新成員
member.no = i;
member.name = _name[r.Next(0,10)];
member.member_class = _member_class[r.Next(0, 3)];
_group.Add(member); //將成員加入List中
richTextBox4.Text += "NO"+member.no+" name: "+member.name+" Class:
"+member.member_class+"\n";
}
}
private void query()
{
richTextBox1.Text = "";
richTextBox2.Text = "";
richTextBox3.Text = "";
combobox CB1 = (combobox)this.comboBox1.SelectedItem;
combobox CB2 = (combobox)this.comboBox2.SelectedItem;
combobox CB3 = (combobox)this.comboBox3.SelectedItem;
var find = from data in this._group //從 _group中尋找data
where data.name == CB1.value //條件為 name = 輸入值
select data; //找出資料
foreach (var item in find)
{
richTextBox1.Text += "name:" + item.name + " NO" + item.no +
"\n" + "========================" + "\n";
}
find = from data in this._group
where (data.no >= Int32.Parse(CB2.value) && data.name == CB1.value)
select data;
foreach (var item in find)
{
richTextBox2.Text += "name:" + item.name + " NO" + item.no +
"\n" + "========================" + "\n";
}
//從 _group中尋找data
find = from data in this._group
//條件為 NO >= 輸入值且 member_class = 輸入值
where (data.no >= Int32.Parse(CB2.value) &
data.member_class == CB3.value)
//找出資料
select data;
foreach (var item in find)
{
richTextBox3.Text += "name:" + item.name + " NO" + item.no + " Class:" +
item.member_class +
"\n" + "========================" + "\n";
}
}
private void btn_query_Click(object sender, EventArgs e)
{
query();
}
private void button1_Click(object sender, EventArgs e)
{
richTextBox4.Text = "";
_group.Clear();
generate_member();
}
}
}