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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 using Reflection;
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10
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11 class FirstSingleBuilder : MethodCallBuilder
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12 {
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13 public static string[] MethodNames = new[] { "First", "FirstOrDefault", "Single", "SingleOrDefault" };
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14
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15 protected override bool CanBuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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16 {
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17 return
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18 methodCall.IsQueryable(MethodNames) &&
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19 methodCall.Arguments.Count == 1;
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20 }
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21
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22 protected override IBuildContext BuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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23 {
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24 var sequence = builder.BuildSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]));
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25 var take = 0;
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26
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27 if (!buildInfo.IsSubQuery || builder.SqlProvider.IsSubQueryTakeSupported)
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28 switch (methodCall.Method.Name)
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29 {
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30 case "First" :
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31 case "FirstOrDefault" :
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32 take = 1;
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33 break;
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34
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35 case "Single" :
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36 case "SingleOrDefault" :
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37 if (!buildInfo.IsSubQuery)
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38 take = 2;
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39 break;
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40 }
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41
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42 if (take != 0)
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43 builder.BuildTake(sequence, new SqlValue(take));
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44
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45 return new FirstSingleContext(buildInfo.Parent, sequence, methodCall);
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46 }
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47
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48 protected override SequenceConvertInfo Convert(
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49 ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo, ParameterExpression param)
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50 {
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51 if (methodCall.Arguments.Count == 2)
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52 {
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53 var predicate = (LambdaExpression)methodCall.Arguments[1].Unwrap();
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54 var info = builder.ConvertSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]), predicate.Parameters[0]);
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55
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56 if (info != null)
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57 {
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58 info.Expression = methodCall.Convert(ex => ConvertMethod(methodCall, 0, info, predicate.Parameters[0], ex));
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59 info.Parameter = param;
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60
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61 return info;
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62 }
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63 }
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64 else
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65 {
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66 var info = builder.ConvertSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]), null);
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67
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68 if (info != null)
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69 {
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70 info.Expression = methodCall.Convert(ex => ConvertMethod(methodCall, 0, info, null, ex));
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71 info.Parameter = param;
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72
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73 return info;
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74 }
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75 }
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76
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77 return null;
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78 }
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79
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80 public class FirstSingleContext : SequenceContextBase
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81 {
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82 public FirstSingleContext(IBuildContext parent, IBuildContext sequence, MethodCallExpression methodCall)
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83 : base(parent, sequence, null)
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84 {
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85 _methodCall = methodCall;
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86 }
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87
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88 readonly MethodCallExpression _methodCall;
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89
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90 public override void BuildQuery<T>(Query<T> query, ParameterExpression queryParameter)
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91 {
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92 Sequence.BuildQuery(query, queryParameter);
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93
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94 switch (_methodCall.Method.Name)
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95 {
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96 case "First" : query.GetElement = (ctx, db, expr, ps) => query.GetIEnumerable(ctx, db, expr, ps).First(); break;
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97 case "FirstOrDefault" : query.GetElement = (ctx, db, expr, ps) => query.GetIEnumerable(ctx, db, expr, ps).FirstOrDefault(); break;
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98 case "Single" : query.GetElement = (ctx, db, expr, ps) => query.GetIEnumerable(ctx, db, expr, ps).Single(); break;
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99 case "SingleOrDefault" : query.GetElement = (ctx, db, expr, ps) => query.GetIEnumerable(ctx, db, expr, ps).SingleOrDefault(); break;
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100 }
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101 }
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102
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103 static object SequenceException()
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104 {
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105 return new object[0].First();
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106 }
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107
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108 public override Expression BuildExpression(Expression expression, int level)
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109 {
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110 if (expression == null)
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111 {
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112 if (Builder.SqlProvider.IsApplyJoinSupported && Parent.SqlQuery.GroupBy.IsEmpty)
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113 {
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114 var join = SqlQuery.OuterApply(SqlQuery);
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115
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116 Parent.SqlQuery.From.Tables[0].Joins.Add(join.JoinedTable);
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117
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118 var expr = Sequence.BuildExpression(expression, level);
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119 var idx = SqlQuery.Select.Add(new SqlValue(1));
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120
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121 idx = ConvertToParentIndex(idx, this);
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122
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123 var defaultValue = _methodCall.Method.Name.EndsWith("OrDefault") ?
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124 Expression.Constant(TypeHelper.GetDefaultValue(expr.Type), expr.Type) as Expression :
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125 Expression.Convert(
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126 Expression.Call(
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127 null,
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128 ReflectionHelper.Expressor<object>.MethodExpressor(_ => SequenceException())),
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129 expr.Type);
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130
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131 expr = Expression.Condition(
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132 Expression.Call(
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133 ExpressionBuilder.DataReaderParam,
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134 ReflectionHelper.DataReader.IsDBNull,
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135 Expression.Constant(idx)),
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136 defaultValue,
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137 expr);
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138
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139 return expr;
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140 }
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141
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142 if (Sequence.IsExpression(null, level, RequestFor.Object).Result)
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143 return Builder.BuildMultipleQuery(Parent, _methodCall);
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144
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145 return Builder.BuildSql(_methodCall.Type, Parent.SqlQuery.Select.Add(SqlQuery));
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146 }
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147
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148 throw new InvalidOperationException();
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149 }
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150
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151 public override SqlInfo[] ConvertToSql(Expression expression, int level, ConvertFlags flags)
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152 {
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153 return Sequence.ConvertToSql(expression, level + 1, flags);
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154 }
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155
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156 public override SqlInfo[] ConvertToIndex(Expression expression, int level, ConvertFlags flags)
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157 {
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158 return Sequence.ConvertToIndex(expression, level, flags);
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159 }
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160
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161 public override IsExpressionResult IsExpression(Expression expression, int level, RequestFor requestFlag)
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162 {
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163 return Sequence.IsExpression(expression, level, requestFlag);
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164 }
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165
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166 public override IBuildContext GetContext(Expression expression, int level, BuildInfo buildInfo)
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167 {
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168 throw new InvalidOperationException();
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169 }
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170 }
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171 }
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172 }
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