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54 lines
3.4 KiB
54 lines
3.4 KiB
// Author: Gockner, Simon
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// Created: 2019-07-02
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// Copyright(c) 2019 SimonG. All Rights Reserved.
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using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace LightweightIocContainer
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{
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internal static class EnumerableExtension
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{
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/// <summary>
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/// Returns the first element of a <see cref="IEnumerable{T}"/>, or a new instance of a given <see cref="Type"/> if the <see cref="IEnumerable{T}"/> contains no elements
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/// </summary>
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/// <typeparam name="TSource">The source <see cref="Type"/> of the <see cref="IEnumerable{T}"/></typeparam>
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/// <typeparam name="TGiven">The given <see cref="Type"/> to return if the <see cref="IEnumerable{T}"/> contains no elements</typeparam>
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/// <param name="source">The given <see cref="IEnumerable{T}"/></param>
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/// <returns>The first element of the <see cref="IEnumerable{T}"/>, or a new instance of a given <see cref="Type"/> if the <see cref="IEnumerable{T}"/> contains no elements</returns>
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public static TSource FirstOrGiven<TSource, TGiven>(this IEnumerable<TSource> source) where TGiven : TSource, new() =>
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source.TryGetFirst<TSource, TGiven>(null);
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/// <summary>
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/// Returns the first element of a <see cref="IEnumerable{T}"/> that satisfies a condition, or a new instance of a given <see cref="Type"/> if no such element is found
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/// </summary>
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/// <typeparam name="TSource">The source <see cref="Type"/> of the <see cref="IEnumerable{T}"/></typeparam>
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/// <typeparam name="TGiven">The given <see cref="Type"/> to return if the <see cref="IEnumerable{T}"/> contains no element that satisfies the given condition</typeparam>
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/// <param name="source">The given <see cref="IEnumerable{T}"/></param>
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/// <param name="predicate">A function to test each element for a condition</param>
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/// <returns>The first element of the <see cref="IEnumerable{T}"/> that satisfies a condition, or a new instance of the given <see cref="Type"/> if no such element is found</returns>
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public static TSource FirstOrGiven<TSource, TGiven>(this IEnumerable<TSource> source, Func<TSource, bool> predicate) where TGiven : TSource, new() =>
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source.TryGetFirst<TSource, TGiven>(predicate);
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/// <summary>
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/// Tries to get the first element of the given <see cref="IEnumerable{T}"/> or creates a new element of a given <see cref="Type"/> when no element is found
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/// </summary>
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/// <typeparam name="TSource">The source <see cref="Type"/> of the <see cref="IEnumerable{T}"/></typeparam>
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/// <typeparam name="TGiven">The given <see cref="Type"/> to create a new element when no fitting element is found</typeparam>
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/// <param name="source">The given <see cref="IEnumerable{T}"/></param>
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/// <param name="predicate">A function to test each element for a condition</param>
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/// <returns>The first element of the <see cref="IEnumerable{T}"/> or a new instance of the given <see cref="Type"/> when no element is found</returns>
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private static TSource TryGetFirst<TSource, TGiven>(this IEnumerable<TSource> source, Func<TSource, bool> predicate) where TGiven : TSource, new()
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{
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try
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{
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return predicate == null ? source.First() : source.First(predicate);
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}
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catch (Exception)
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{
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return new TGiven();
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}
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}
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}
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} |