mirror of https://github.com/dahall/Vanara.git
Added VirtualList class similar to VirtualDictionary
David Hall
parent
e7d92752e7
commit
236e881436
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using System.Collections;
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using System.Collections.Generic;
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using System.Diagnostics.CodeAnalysis;
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namespace Vanara.Collections;
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/// <summary>Interface that defines the methods for a virtual list. This interface is used by the <see cref="VirtualList{T}"/> class.</summary>
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/// <typeparam name="T">The type of the element.</typeparam>
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/// <seealso cref="IVirtualReadOnlyListMethods<T>"/>
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public interface IVirtualListMethods<T> : IVirtualReadOnlyListMethods<T>
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{
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/// <summary>Adds an item to the end of the list.</summary>
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/// <param name="item">The object to add to the list.</param>
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void AddItem(T item);
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/// <summary>Inserts an item to the list at the specified index.</summary>
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/// <param name="index">The zero-based index at which item should be inserted.</param>
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/// <param name="item">The object to insert into the list.</param>
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void InsertItemAt(int index, T item);
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/// <summary>Removes the item at the specified index.</summary>
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/// <param name="index">The zero-based index of the item to remove.</param>
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void RemoveItemAt(int index);
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/// <summary>Sets the element at the specified index.</summary>
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/// <param name="index">The zero-based index of the element to set.</param>
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/// <param name="value">The element at the specified index.</param>
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void SetItemAt(int index, T value);
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}
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/// <summary>
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/// Interface that defines the methods for a virtual read-only list. This interface is used by the <see cref="VirtualReadOnlyList{T}"/> class.
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/// </summary>
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/// <typeparam name="T">The type of the element.</typeparam>
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public interface IVirtualReadOnlyListMethods<T>
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{
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/// <summary>Gets the number of elements in the collection.</summary>
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/// <returns>The number of elements in the collection.</returns>
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int GetItemCount();
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/// <summary>Tries to get the element at the specified index.</summary>
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/// <param name="index">The zero-based index of the element to get.</param>
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/// <param name="value">The value, if <paramref name="index"/> is a valid index; or <see langword="default"/> if not.</param>
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/// <returns><see langword="true"/> if the list contains an element at the specified index; otherwise, <see langword="false"/>.</returns>
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bool TryGet(int index, [NotNullWhen(true)] out T? value);
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}
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/// <summary>A virtual list that implements a lot of the scaffolding.</summary>
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/// <typeparam name="T">The element type.</typeparam>
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public class VirtualList<T> : VirtualReadOnlyList<T>, IList<T>
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{
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/// <summary>The implementation.</summary>
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protected readonly IVirtualListMethods<T> impl;
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/// <summary>Initializes a new instance of the <see cref="VirtualList{T}"/> class.</summary>
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public VirtualList(IVirtualListMethods<T> impl) : base(impl) => this.impl = impl;
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/// <inheritdoc/>
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bool ICollection<T>.IsReadOnly => false;
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/// <inheritdoc/>
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public new T this[int index]
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{
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get => base[index];
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set => impl.SetItemAt(index, value);
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}
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/// <inheritdoc/>
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public void Add(T item) => impl.AddItem(item);
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/// <inheritdoc/>
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public void Clear()
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{
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for (int i = Count - 1; i >= 0; i--)
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RemoveAt(i);
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}
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/// <inheritdoc/>
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public void Insert(int index, T item) => impl.InsertItemAt(index, item);
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/// <inheritdoc/>
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public bool Remove(T item)
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{
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int i = IndexOf(item);
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if (i >= 0)
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{
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RemoveAt(i);
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return true;
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}
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return false;
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}
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/// <inheritdoc/>
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public void RemoveAt(int index) => impl.RemoveItemAt(index);
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/// <inheritdoc/>
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IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
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}
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/// <summary>Wrapper for <see cref="IVirtualListMethods{T}"/> that allows for the use of delegates instead of implementing the interface.</summary>
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/// <typeparam name="T">The element type.</typeparam>
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/// <seealso cref="IVirtualListMethods<T>"/>
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public class VirtualListMethodCarrier<T> : IVirtualListMethods<T>
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{
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/// <summary>Initializes a new instance of the <see cref="VirtualListMethodCarrier{T}"/> class.</summary>
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/// <param name="tryGet">Delegate that tries to get the element at the specified index.</param>
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/// <param name="getCount">Delegate that gets the number of elements in the collection.</param>
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/// <param name="add">Delegate that adds an item to the end of the list.</param>
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/// <param name="insert">Delegate that inserts an item to the list at the specified index.</param>
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/// <param name="removeAt">Delegate that removes the item at the specified index.</param>
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/// <param name="setAt">Delegate that sets the element at the specified index.</param>
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public VirtualListMethodCarrier(VirtualReadOnlyList<T>.TryGetDelegate tryGet, Func<int> getCount, Action<T>? add = null, Action<int, T>? insert = null, Action<int>? removeAt = null, Action<int, T>? setAt = null)
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{
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TryGet = tryGet;
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GetCount = getCount;
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Add = add;
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Insert = insert;
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RemoveAt = removeAt;
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SetAt = setAt;
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}
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/// <summary>Delegate that adds an item to the end of the list.</summary>
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public Action<T>? Add { get; }
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/// <summary>Delegate that gets the number of elements in the collection.</summary>
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public Func<int> GetCount { get; }
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/// <summary>Delegate that inserts an item to the list at the specified index.</summary>
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public Action<int, T>? Insert { get; }
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/// <summary>Delegate that removes the item at the specified index.</summary>
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public Action<int>? RemoveAt { get; }
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/// <summary>Delegate that sets the element at the specified index.</summary>
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public Action<int, T>? SetAt { get; }
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/// <summary>Delegate that tries to get the element at the specified index.</summary>
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public VirtualReadOnlyList<T>.TryGetDelegate TryGet { get; }
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/// <inheritdoc/>
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void IVirtualListMethods<T>.AddItem(T item) => Add?.Invoke(item);
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/// <inheritdoc/>
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int IVirtualReadOnlyListMethods<T>.GetItemCount() => GetCount();
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/// <inheritdoc/>
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void IVirtualListMethods<T>.InsertItemAt(int index, T item) => Insert?.Invoke(index, item);
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/// <inheritdoc/>
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void IVirtualListMethods<T>.RemoveItemAt(int index) => RemoveAt?.Invoke(index);
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/// <inheritdoc/>
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void IVirtualListMethods<T>.SetItemAt(int index, T value) => SetAt?.Invoke(index, value);
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/// <inheritdoc/>
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bool IVirtualReadOnlyListMethods<T>.TryGet(int index, [NotNullWhen(true)] out T? value) => TryGet(index, out value);
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}
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/// <summary>A virtual read-only list that implements a lot of the scaffolding.</summary>
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/// <typeparam name="T">The element type.</typeparam>
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public class VirtualReadOnlyList<T> : IReadOnlyList<T>
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{
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/// <summary>The read only implementation.</summary>
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protected readonly IVirtualReadOnlyListMethods<T> readOnlyImpl;
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/// <summary>Initializes a new instance of the <see cref="VirtualList{T}"/> class.</summary>
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public VirtualReadOnlyList(IVirtualReadOnlyListMethods<T> impl) => readOnlyImpl = impl;
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/// <summary>Delegate for a method that tries to get the element at the specified index.</summary>
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/// <param name="index">The zero-based index of the element to get.</param>
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/// <param name="value">The value, if <paramref name="index"/> is a valid index; or <see langword="default"/> if not.</param>
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/// <returns><see langword="true"/> if the list contains an element at the specified index; otherwise, <see langword="false"/>.</returns>
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public delegate bool TryGetDelegate(int index, [NotNullWhen(true)] out T? value);
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/// <inheritdoc/>
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public virtual int Count => readOnlyImpl.GetItemCount();
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/// <inheritdoc/>
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public virtual T this[int index] => readOnlyImpl.TryGet(index, out T? v) ? v : throw new ArgumentOutOfRangeException(nameof(index));
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/// <inheritdoc/>
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public virtual bool Contains(T item) => IndexOf(item) >= 0;
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/// <inheritdoc/>
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public virtual void CopyTo(T[] array, int arrayIndex)
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{
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if (array is null)
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throw new ArgumentNullException(nameof(array));
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if (arrayIndex < 0 || arrayIndex > array.Length)
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throw new ArgumentOutOfRangeException(nameof(arrayIndex));
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if (array.Length - arrayIndex < Count)
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throw new ArgumentException("The number of elements in the source ICollection<T> is greater than the available space from arrayIndex to the end of the destination array.");
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for (int i = 0; i < Count; i++)
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array[arrayIndex + i] = this[i];
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}
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/// <inheritdoc/>
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public virtual IEnumerator<T> GetEnumerator()
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{
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for (int i = 0; i < Count; i++)
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yield return this[i];
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}
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/// <inheritdoc/>
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public virtual int IndexOf(T item)
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{
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for (int i = 0; i < Count; i++)
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{
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/* Unmerged change from project 'Vanara.PInvoke.Printing (net48)'
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Before:
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if (Equals(this[i], item))
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After:
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{
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if (Equals(this[i], item))
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*/
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if (Equals(this[i], item))
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return i;
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}
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/* Unmerged change from project 'Vanara.PInvoke.Printing (net48)'
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Before:
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return -1;
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After:
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}
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return -1;
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*/
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return -1;
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}
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/// <inheritdoc/>
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IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
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}
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