120 lines
3.7 KiB
C#
120 lines
3.7 KiB
C#
using System.Collections;
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using System.Collections.Generic;
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using System.Drawing;
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using System.Linq;
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namespace System.Windows.Forms;
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/// <summary>ComboBox 和 ListBox 的共同基类：列表项、选中项</summary>
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public abstract class ListControl : Control
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{
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/// <summary>选中项的序号。列表项增删时直接调整（和 WinForms 一样不触发 SelectedIndexChanged）</summary>
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private protected int SelectedIndexValue = -1;
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private protected override Color? OwnBackColor => SystemColors.Window;
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private protected override Color? OwnForeColor => SystemColors.WindowText;
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private protected override bool SupportsTransparentBackColor => false;
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public abstract int SelectedIndex { get; set; }
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public string DisplayMember { get; set; } = "";
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public string ValueMember { get; set; } = "";
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public event EventHandler? SelectedValueChanged;
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protected virtual void OnSelectedValueChanged(EventArgs e) => SelectedValueChanged?.Invoke(this, e);
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public string GetItemText(object? item) => item?.ToString() ?? "";
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/// <summary>列表项变化后调用：把新的列表和选中项发给浏览器</summary>
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internal abstract void ItemsChanged();
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/// <summary>Items.Clear() 时调用：先取消选中，再刷新列表</summary>
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internal abstract void ItemsCleared();
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internal void ItemInserted(int index)
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{
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if (SelectedIndexValue >= index) SelectedIndexValue++;
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ItemsChanged();
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}
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/// <summary>删掉的正是选中项时取消选中，删掉前面的项时选中项序号前移</summary>
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internal void ItemRemoved(int index)
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{
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if (SelectedIndexValue == index) SelectedIndexValue = -1;
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else if (SelectedIndexValue > index) SelectedIndexValue--;
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ItemsChanged();
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}
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protected string[] ItemTexts(IEnumerable<object?> items) => items.Select(GetItemText).ToArray();
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}
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/// <summary>ComboBox.ObjectCollection 和 ListBox.ObjectCollection 共用的实现</summary>
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public abstract class ListItemCollection : IList, IEnumerable<object?>
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{
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private readonly List<object?> _items = new();
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private readonly ListControl _owner;
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private protected ListItemCollection(ListControl owner) => _owner = owner;
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public int Count => _items.Count;
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public bool IsReadOnly => false;
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bool IList.IsFixedSize => false;
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bool ICollection.IsSynchronized => false;
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object ICollection.SyncRoot => this;
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public object? this[int index]
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{
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get => _items[index];
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set
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{
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_items[index] = value;
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_owner.ItemsChanged();
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}
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}
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public int Add(object? item)
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{
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if (item == null) throw new ArgumentNullException(nameof(item), "值不能为 null。");
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_items.Add(item);
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_owner.ItemsChanged();
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return _items.Count - 1;
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}
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public void AddRange(object[] items)
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{
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_items.AddRange(items);
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_owner.ItemsChanged();
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}
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public void Insert(int index, object? item)
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{
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_items.Insert(index, item);
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_owner.ItemInserted(index);
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}
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public void Remove(object? item)
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{
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var index = _items.IndexOf(item);
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if (index >= 0) RemoveAt(index);
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}
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public void RemoveAt(int index)
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{
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_items.RemoveAt(index);
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_owner.ItemRemoved(index);
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}
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public void Clear()
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{
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_items.Clear();
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_owner.ItemsCleared();
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}
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public bool Contains(object? item) => _items.Contains(item);
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public int IndexOf(object? item) => _items.IndexOf(item);
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public void CopyTo(Array array, int index) => ((ICollection)_items).CopyTo(array, index);
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public IEnumerator<object?> GetEnumerator() => _items.GetEnumerator();
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IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
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}
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