C# HashTable implement on ListView

作者：貓貓風 ?●ω●?│2019-09-16 16:20:34│巴幣：18│人氣：415

雜湊表（Hash table，也叫哈希表），是根據鍵（Key）而直接查詢在內存存儲位置的資料結構。也就是說，它通過計算一個關於鍵值的函數，將所需查詢的數據映射到表中一個位置來查詢記錄，這加快了查找速度。這個映射函數稱做雜湊函數，存放記錄的數組稱做雜湊表。

此篇主要以 ListView 來呈現從Hash table(雜湊表)中尋找內存的資料

預先在雜湊表中存入以下資料，從雜湊表中根據KEY選取資料並訂出資料架構

資料架構如下一個區域有五個物件，每個物件個別有其數量

根據下圖從雜湊表找出資料並篩選出個別類型物件的數量

實作程式碼如下

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;
using System.Collections;
using System.Threading;
namespace HashTable_example
{
public partial class Form1 : Form
{
//設定 console輸出
[System.Runtime.InteropServices.DllImport("kernel32.dll", SetLastError = true)]
static extern bool AllocConsole();
[System.Runtime.InteropServices.DllImport("Kernel32")]
public static extern void FreeConsole();
public Form1()
{
InitializeComponent();
}
Hashtable _all = new Hashtable();
Hashtable _fish = new Hashtable();
Hashtable _cat = new Hashtable();
Hashtable _mountain = new Hashtable();
Hashtable _tree = new Hashtable();
Hashtable _lake = new Hashtable();
private void Form1_Load(object sender, EventArgs e)
{
//定義 listview 欄位與型態
listView1.GridLines = true;
listView1.FullRowSelect = true;
listView1.View = View.Details;
listView1.Scrollable = true;
listView1.MultiSelect = false; // 不可以多行選擇
listView1.HeaderStyle = ColumnHeaderStyle.Nonclickable;
listView1.Columns.Add("Fish", 100, HorizontalAlignment.Right);
listView1.Columns.Add("Cat", 100, HorizontalAlignment.Left);
listView1.Columns.Add("Mountain", 120, HorizontalAlignment.Left);
listView1.Columns.Add("Tree", 100, HorizontalAlignment.Left);
listView1.Columns.Add("Lake", 100, HorizontalAlignment.Left);
listView1.Visible = true;
listView2.GridLines = true;
listView2.FullRowSelect = true;
listView2.View = View.Details;
listView2.Scrollable = true;
listView2.MultiSelect = false; // 不可以多行選擇
listView2.HeaderStyle = ColumnHeaderStyle.Nonclickable;
listView2.Visible = true;
String[] item_content = new String[5]; //宣告行數
ListViewItem item; // 宣告項目
//加入雜湊資料
_all.Add("Fish", 5);
_all.Add("Cat", 3);
_all.Add("Mountain", 3);
_all.Add("Tree", 5);
_all.Add("Lake", 2);
_fish.Add("Grass carp", 142);
_fish.Add("Peruvian anchoveta", 200);
_fish.Add("Silver carp", 385);
_fish.Add("Common carp", 499);
_fish.Add("Alaska pollock", 56);
_cat.Add("Abyssinian", 151);
_cat.Add("American Bobtail", 33);
_cat.Add("Balinese-Javanese ", 42);
_mountain.Add("Everest", 1);
_mountain.Add("Kangchenjunga", 1);
_mountain.Add("Lhotse", 1);
_tree.Add("Tulsi Plant", 1120);
_tree.Add("Amla Plant", 932);
_tree.Add("Eucalyptus", 421);
_tree.Add("Mahagony", 563);
_tree.Add("Aloe Vera", 116);
_lake.Add("Finn", 1);
_lake.Add("Austen", 1);
//AllocConsole(); //啟用 console輸出
int index = 0;
//將雜湊資料顯示在listview上
while (index < _all.Count) //每列進行比較找到當前欄位最大值表示結束
{
//如果在雜湊中有找到當前欄位符合標頭，將標頭所屬資料加入 listview中
foreach (DictionaryEntry member in _all)
{
if (member.Key.ToString() == listView1.Columns[index].Text)
{
item_content[index] = member.Value.ToString();
index++;
break;
}
}
}
//將資料加入項目
item = new ListViewItem(item_content);
//將項目加入listview
listView1.Items.Add(item);
}
private void listView1_Click(object sender, EventArgs e)
{
Point mousePos = listView1.PointToClient(Control.MousePosition);
ListViewHitTestInfo hitTest = listView1.HitTest(mousePos);
int columnIndex = hitTest.Item.SubItems.IndexOf(hitTest.SubItem);
txt_selected_item.Text = listView1.Items[0].SubItems[columnIndex].Text;
txt_selected_value.Text = listView1.Columns[columnIndex].Text;
Hashtable select = new Hashtable();
if (txt_selected_value.Text == "Fish") { select = _fish; }
else if (txt_selected_value.Text == "Cat") { select = _cat; }
else if (txt_selected_value.Text == "Mountain") { select = _mountain; }
else if (txt_selected_value.Text == "Tree") { select = _tree; }
else { select = _lake; }
listView2.Clear();
foreach (DictionaryEntry member in select)
{
listView2.Columns.Add(member.Key.ToString(), 100,
HorizontalAlignment.Right);
}
String[] item_content = new String[5]; //宣告行數
ListViewItem item; // 宣告項目
int index = 0;
//將雜湊資料顯示在listview上
while (index < select.Count) //每列進行比較找到當前欄位最大值表示結束
{
//如果在雜湊中有找到當前欄位符合標頭，將標頭所屬資料加入 listview中
foreach (DictionaryEntry member in select)
{
if (member.Key.ToString() == listView2.Columns[index].Text)
{
listView2.Columns[index].TextAlign = HorizontalAlignment.Center;
item_content[index] = member.Value.ToString();
index++;
break;
}
}
}
//將資料加入項目
item = new ListViewItem(item_content);
//將項目加入listview
listView2.Items.Add(item);
AutoSizeColumnList(listView2);
}
//自動對齊 ListView 依據標題長度和listview大小
private void AutoSizeColumnList(ListView listView)
{
//Prevents flickering
listView.BeginUpdate();
Dictionary<int, int> columnSize = new Dictionary<int, int>();
//Auto size using header
listView.AutoResizeColumns(ColumnHeaderAutoResizeStyle.HeaderSize);
//Grab column size based on header
foreach (ColumnHeader colHeader in listView.Columns)
columnSize.Add(colHeader.Index, colHeader.Width);
//Auto size using data
listView.AutoResizeColumns(ColumnHeaderAutoResizeStyle.ColumnContent);
//Grab comumn size based on data and set max width
foreach (ColumnHeader colHeader in listView.Columns)
{
int nColWidth;
if (columnSize.TryGetValue(colHeader.Index, out nColWidth))
colHeader.Width = Math.Max(nColWidth, colHeader.Width);
else
//Default to 50
colHeader.Width = Math.Max(50, colHeader.Width);
}
listView.EndUpdate();
}
}
}