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1 using System;
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2 using System.Linq;
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3 using System.Linq.Expressions;
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4
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5 namespace BLToolkit.Data.Linq.Builder
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6 {
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7 using BLToolkit.Linq;
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8 using Data.Sql;
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9
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10 class DefaultIfEmptyBuilder : MethodCallBuilder
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11 {
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12 protected override bool CanBuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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13 {
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14 return methodCall.IsQueryable("DefaultIfEmpty");
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15 }
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16
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17 protected override IBuildContext BuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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18 {
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19 var sequence = builder.BuildSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]));
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20 var defaultValue = methodCall.Arguments.Count == 1 ? null : methodCall.Arguments[1].Unwrap();
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21
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22 if (buildInfo.Parent is SelectManyBuilder.SelectManyContext)
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23 {
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24 var groupJoin = ((SelectManyBuilder.SelectManyContext)buildInfo.Parent).Sequence[0] as JoinBuilder.GroupJoinContext;
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25
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26 if (groupJoin != null)
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27 {
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28 groupJoin.SqlQuery.From.Tables[0].Joins[0].JoinType = SqlQuery.JoinType.Left;
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29 groupJoin.SqlQuery.From.Tables[0].Joins[0].IsWeak = false;
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30 }
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31 }
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32
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33 return new DefaultIfEmptyContext(buildInfo.Parent, sequence, defaultValue);
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34 }
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35
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36 protected override SequenceConvertInfo Convert(
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37 ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo, ParameterExpression param)
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38 {
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39 return null;
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40 }
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41
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42 public class DefaultIfEmptyContext : SequenceContextBase
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43 {
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44 public DefaultIfEmptyContext(IBuildContext parent, IBuildContext sequence, Expression defaultValue)
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45 : base(parent, sequence, null)
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46 {
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47 _defaultValue = defaultValue;
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48 }
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49
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50 private readonly Expression _defaultValue;
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51
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52 public override Expression BuildExpression(Expression expression, int level)
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53 {
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54 var expr = Sequence.BuildExpression(expression, level);
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55
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56 if (expression == null)
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57 {
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58 var q =
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59 from col in SqlQuery.Select.Columns
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60 where !col.CanBeNull()
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61 select SqlQuery.Select.Columns.IndexOf(col);
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62
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63 var idx = q.DefaultIfEmpty(-1).First();
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64
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65 if (idx == -1)
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66 idx = SqlQuery.Select.Add(new SqlValue((int?) 1));
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67
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68 var n = ConvertToParentIndex(idx, this);
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69
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70 var e = Expression.Call(
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71 ExpressionBuilder.DataReaderParam,
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72 ReflectionHelper.DataReader.IsDBNull,
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73 Expression.Constant(n)) as Expression;
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74
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75 var defaultValue = _defaultValue ?? Expression.Constant(null, expr.Type);
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76
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77 #if FW4 || SILVERLIGHT
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78
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79 if (expr.NodeType == ExpressionType.Parameter)
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80 {
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81 var par = (ParameterExpression)expr;
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82 var pidx = Builder.BlockVariables.IndexOf(par);
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83
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84 if (pidx >= 0)
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85 {
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86 var ex = Builder.BlockExpressions[pidx];
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87
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88 if (ex.NodeType == ExpressionType.Assign)
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89 {
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90 var bex = (BinaryExpression)ex;
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91
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92 if (bex.Left == expr)
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93 {
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94 if (bex.Right.NodeType != ExpressionType.Conditional)
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95 {
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96 Builder.BlockExpressions[pidx] =
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97 Expression.Assign(
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98 bex.Left,
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99 Expression.Condition(e, defaultValue, bex.Right));
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100 }
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101 }
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102 }
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103 }
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104 }
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105
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106 #endif
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107
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108 expr = Expression.Condition(e, defaultValue, expr);
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109 }
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110
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111 return expr;
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112 }
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113
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114 public override SqlInfo[] ConvertToSql(Expression expression, int level, ConvertFlags flags)
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115 {
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116 return Sequence.ConvertToSql(expression, level, flags);
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117 }
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118
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119 public override SqlInfo[] ConvertToIndex(Expression expression, int level, ConvertFlags flags)
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120 {
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121 return Sequence.ConvertToIndex(expression, level, flags);
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122 }
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123
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124 public override IsExpressionResult IsExpression(Expression expression, int level, RequestFor requestFlag)
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125 {
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126 return Sequence.IsExpression(expression, level, requestFlag);
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127 }
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128
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129 public override IBuildContext GetContext(Expression expression, int level, BuildInfo buildInfo)
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130 {
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131 return Sequence.GetContext(expression, level, buildInfo);
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132 }
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133 }
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134 }
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135 }
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