92 lines
4.7 KiB
C#
92 lines
4.7 KiB
C#
/*
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* DynamORM - Dynamic Object-Relational Mapping library.
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* Copyright (c) 2012-2015, Grzegorz Russek (grzegorz.russek@gmail.com)
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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using System;
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using System.Collections.Generic;
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namespace DynamORM.Helpers
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{
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/// <summary>Class contains unclassified extensions.</summary>
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internal static class UnclassifiedExtensions
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{
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/// <summary>Easy way to use conditional value.</summary>
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/// <remarks>Includes <see cref="DBNull.Value"/>.</remarks>
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/// <typeparam name="T">Input object type to check.</typeparam>
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/// <typeparam name="R">Result type.</typeparam>
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/// <param name="obj">The object to check.</param>
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/// <param name="func">The select function.</param>
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/// <param name="elseValue">The else value.</param>
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/// <returns>Selected value or default value.</returns>
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/// <example>It lets you do this:
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/// <code>var lname = thingy.NullOr(t => t.Name).NullOr(n => n.ToLower());</code>
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/// which is more fluent and (IMO) easier to read than this:
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/// <code>var lname = (thingy != null ? thingy.Name : null) != null ? thingy.Name.ToLower() : null;</code>
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/// </example>
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public static R NullOr<T, R>(this T obj, Func<T, R> func, R elseValue = default(R)) where T : class
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{
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return obj != null && obj != DBNull.Value ?
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func(obj) : elseValue;
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}
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/// <summary>Easy way to use conditional value.</summary>
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/// <remarks>Includes <see cref="DBNull.Value"/>.</remarks>
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/// <typeparam name="T">Input object type to check.</typeparam>
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/// <typeparam name="R">Result type.</typeparam>
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/// <param name="obj">The object to check.</param>
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/// <param name="func">The select function.</param>
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/// <param name="elseFunc">The else value function.</param>
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/// <returns>Selected value or default value.</returns>
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/// <example>It lets you do this:
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/// <code>var lname = thingy.NullOr(t => t.Name).NullOr(n => n.ToLower());</code>
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/// which is more fluent and (IMO) easier to read than this:
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/// <code>var lname = (thingy != null ? thingy.Name : null) != null ? thingy.Name.ToLower() : null;</code>
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/// </example>
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public static R NullOrFn<T, R>(this T obj, Func<T, R> func, Func<R> elseFunc = null) where T : class
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{
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// Old if to avoid recurency.
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return obj != null && obj != DBNull.Value ?
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func(obj) : elseFunc != null ? elseFunc() : default(R);
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}
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#if !NET6_0_OR_GREATER
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/// <summary>Simple distinct by selector extension.</summary>
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/// <returns>The enumerator of elements distinct by specified selector.</returns>
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/// <param name="source">Source collection.</param>
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/// <param name="keySelector">Distinct key selector.</param>
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/// <typeparam name="R">The enumerable element type parameter.</typeparam>
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/// <typeparam name="T">The selector type parameter.</typeparam>
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public static IEnumerable<R> DistinctBy<R, T>(this IEnumerable<R> source, Func<R, T> keySelector)
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{
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HashSet<T> seenKeys = new HashSet<T>();
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foreach (R element in source)
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if (seenKeys.Add(keySelector(element)))
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yield return element;
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}
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#endif
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}
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} |