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1 using System;
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2 using System.Collections.Generic;
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3 using System.Linq;
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4 using System.Linq.Expressions;
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5
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6 namespace BLToolkit.Data.Linq.Builder
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7 {
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8 using BLToolkit.Linq;
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9 using Data.Sql;
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10
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11 class TakeSkipBuilder : MethodCallBuilder
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12 {
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13 protected override bool CanBuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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14 {
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15 return methodCall.IsQueryable("Skip", "Take");
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16 }
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17
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18 protected override IBuildContext BuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo)
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19 {
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20 var sequence = builder.BuildSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]));
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21
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22 var arg = methodCall.Arguments[1].Unwrap();
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23
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24 if (arg.NodeType == ExpressionType.Lambda)
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25 arg = ((LambdaExpression)arg).Body.Unwrap();
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26
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27 var expr = builder.ConvertToSql(sequence, arg, false);
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28
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29 if (methodCall.Method.Name == "Take")
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30 {
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31 BuildTake(builder, sequence, expr);
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32 }
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33 else
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34 {
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35 BuildSkip(builder, sequence, sequence.SqlQuery.Select.SkipValue, expr);
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36 }
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37
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38 return sequence;
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39 }
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40
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41 protected override SequenceConvertInfo Convert(
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42 ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo, ParameterExpression param)
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43 {
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44 var info = builder.ConvertSequence(new BuildInfo(buildInfo, methodCall.Arguments[0]), null);
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45
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46 if (info != null)
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47 {
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48 info.Expression =
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49 Expression.Call(
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50 methodCall.Method.DeclaringType,
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51 methodCall.Method.Name,
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52 new[] { info.Expression.Type.GetGenericArguments()[0] },
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53 info.Expression, methodCall.Arguments[1]);
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54 info.Parameter = param;
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55
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56 return info;
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57 }
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58
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59 return null;
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60 }
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61
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62 static void BuildTake(ExpressionBuilder builder, IBuildContext sequence, ISqlExpression expr)
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63 {
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64 var sql = sequence.SqlQuery;
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65
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66 builder.SqlProvider.SqlQuery = sql;
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67
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68 sql.Select.Take(expr);
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69
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70 if (sql.Select.SkipValue != null && builder.SqlProvider.IsTakeSupported && !builder.SqlProvider.IsSkipSupported)
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71 {
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72 if (sql.Select.SkipValue is SqlParameter && sql.Select.TakeValue is SqlValue)
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73 {
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74 var skip = (SqlParameter)sql.Select.SkipValue;
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75 var parm = (SqlParameter)sql.Select.SkipValue.Clone(new Dictionary<ICloneableElement,ICloneableElement>(), _ => true);
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76
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77 parm.SetTakeConverter((int)((SqlValue)sql.Select.TakeValue).Value);
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78
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79 sql.Select.Take(parm);
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80
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81 var ep = (from pm in builder.CurrentSqlParameters where pm.SqlParameter == skip select pm).First();
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82
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83 ep = new ParameterAccessor
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84 {
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85 Expression = ep.Expression,
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86 Accessor = ep.Accessor,
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87 SqlParameter = parm
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88 };
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89
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90 builder.CurrentSqlParameters.Add(ep);
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91 }
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92 else
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93 sql.Select.Take(builder.Convert(
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94 sequence,
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95 new SqlBinaryExpression(typeof(int), sql.Select.SkipValue, "+", sql.Select.TakeValue, Precedence.Additive)));
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96 }
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97
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98 if (!builder.SqlProvider.TakeAcceptsParameter)
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99 {
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100 var p = sql.Select.TakeValue as SqlParameter;
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101
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102 if (p != null)
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103 p.IsQueryParameter = false;
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104 }
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105 }
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106
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107 static void BuildSkip(ExpressionBuilder builder, IBuildContext sequence, ISqlExpression prevSkipValue, ISqlExpression expr)
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108 {
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109 var sql = sequence.SqlQuery;
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110
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111 builder.SqlProvider.SqlQuery = sql;
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112
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113 sql.Select.Skip(expr);
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114
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115 builder.SqlProvider.SqlQuery = sql;
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116
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117 if (sql.Select.TakeValue != null)
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118 {
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119 if (builder.SqlProvider.IsSkipSupported || !builder.SqlProvider.IsTakeSupported)
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120 sql.Select.Take(builder.Convert(
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121 sequence,
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122 new SqlBinaryExpression(typeof(int), sql.Select.TakeValue, "-", sql.Select.SkipValue, Precedence.Additive)));
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123
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124 if (prevSkipValue != null)
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125 sql.Select.Skip(builder.Convert(
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126 sequence,
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127 new SqlBinaryExpression(typeof(int), prevSkipValue, "+", sql.Select.SkipValue, Precedence.Additive)));
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128 }
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129
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130 if (!builder.SqlProvider.TakeAcceptsParameter)
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131 {
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132 var p = sql.Select.SkipValue as SqlParameter;
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133
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134 if (p != null)
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135 p.IsQueryParameter = false;
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136 }
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137 }
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138 }
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139 }
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