70 lines
2.7 KiB
C#
70 lines
2.7 KiB
C#
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//---------------------------------------------------------------------
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// <copyright file="TrailingSpaceComparer.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//
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// @owner [....]
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// @backupOwner [....]
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//---------------------------------------------------------------------
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using System.Collections.Generic;
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namespace System.Data.Common.Utils
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{
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/// <summary>
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/// Comparer that treats two strings as equivalent if they differ only by trailing
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/// spaces, e.g. 'A' eq 'A '. Useful when determining if a set of values is unique
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/// even given the possibility of padding (consider SQL Server char and nchar columns)
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/// or to lookup values when the set of values is known to honor this uniqueness constraint.
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/// </summary>
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internal class TrailingSpaceComparer : IEqualityComparer<object>
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{
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private TrailingSpaceComparer() { }
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internal readonly static TrailingSpaceComparer Instance = new TrailingSpaceComparer();
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private readonly static IEqualityComparer<object> s_template = EqualityComparer<object>.Default;
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bool IEqualityComparer<object>.Equals(object x, object y)
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{
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string xAsString = x as string;
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if (null != xAsString)
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{
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string yAsString = y as string;
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if (null != yAsString)
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{
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return TrailingSpaceStringComparer.Instance.Equals(xAsString, yAsString);
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}
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}
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return s_template.Equals(x, y);
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}
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int IEqualityComparer<object>.GetHashCode(object obj)
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{
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string value = obj as string;
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if (null != value)
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{
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return TrailingSpaceStringComparer.Instance.GetHashCode(value);
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}
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return s_template.GetHashCode(obj);
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}
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}
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/// <summary>
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/// Typed version of TrailingSpaceComparer.
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/// </summary>
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internal class TrailingSpaceStringComparer : IEqualityComparer<string>
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{
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internal static readonly TrailingSpaceStringComparer Instance = new TrailingSpaceStringComparer();
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private TrailingSpaceStringComparer() { }
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public bool Equals(string x, string y)
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{
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return StringComparer.OrdinalIgnoreCase.Equals(NormalizeString(x), NormalizeString(y));
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}
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public int GetHashCode(string obj)
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{
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return StringComparer.OrdinalIgnoreCase.GetHashCode(NormalizeString(obj));
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}
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internal static string NormalizeString(string value)
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{
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if (null == value || !value.EndsWith(" ", StringComparison.Ordinal)) { return value; }
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else { return value.TrimEnd(' '); }
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}
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}
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}
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