5 // Copyright (c) 2007-2008 Jiri Moudry, Pascal Craponne
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7 // Permission is hereby granted, free of charge, to any person obtaining a copy
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8 // of this software and associated documentation files (the "Software"), to deal
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9 // in the Software without restriction, including without limitation the rights
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10 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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11 // copies of the Software, and to permit persons to whom the Software is
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12 // furnished to do so, subject to the following conditions:
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14 // The above copyright notice and this permission notice shall be included in
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15 // all copies or substantial portions of the Software.
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17 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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18 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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19 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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20 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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21 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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22 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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28 using System.Collections.Generic;
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29 using System.Linq.Expressions;
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30 using DbLinq.Data.Linq.Implementation;
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32 namespace DbLinq.Util
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35 /// IEqualityComparer implementation for Expression
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37 internal class ExpressionEqualityComparer : IEqualityComparer<Expression>
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40 /// Determines whether the specified objects are equal.
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42 /// <param name="x">The first object of type <paramref name="T"/> to compare.</param>
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43 /// <param name="y">The second object of type <paramref name="T"/> to compare.</param>
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45 /// true if the specified objects are equal; otherwise, false.
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47 public bool Equals(Expression x, Expression y)
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49 // both nulls? comparison is OK
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50 if (x == null && y == null)
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53 if (x == null && y != null)
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56 if (x != null && y == null)
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59 // first thing: check types
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60 if (x.GetType() != y.GetType())
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63 // then check node types
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64 if (x.NodeType != y.NodeType)
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67 // finally, check expression types
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68 if (x.Type != y.Type)
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71 return (x.ToString() == y.ToString());
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75 /// Returns a hash code for the specified object.
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77 /// <param name="obj">The <see cref="T:System.Object"/> for which a hash code is to be returned.</param>
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78 /// <returns>A hash code for the specified object.</returns>
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79 /// <exception cref="T:System.ArgumentNullException">
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80 /// The type of <paramref name="obj"/> is a reference type and <paramref name="obj"/> is null.
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82 public int GetHashCode(Expression obj)
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84 return (int)obj.NodeType ^ obj.GetType().GetHashCode();
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