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CSHARP-3713: SelectMany doesn't support DefaultIfEmpty().
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+167
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‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodCallExpressionToAggregationExpressionTranslator.cs

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@@ -33,6 +33,7 @@ public static AggregationExpression Translate(TranslationContext context, Method
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case "CompareTo": return CompareToMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "Concat": return ConcatMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "Contains": return ContainsMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "DefaultIfEmpty": return DefaultIfEmptyMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "Distinct": return DistinctMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "ElementAt": return ElementAtMethodToAggregationExpressionTranslator.Translate(context, expression);
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case "Equals": return EqualsMethodToAggregationExpressionTranslator.Translate(context, expression);

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/DefaultIfEmptyMethodToAggregationExpressionTranslator.cs

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/* Copyright 2010-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Linq.Expressions;
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using MongoDB.Bson;
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using MongoDB.Driver.Linq.Linq3Implementation.Ast.Expressions;
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using MongoDB.Driver.Linq.Linq3Implementation.Misc;
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using MongoDB.Driver.Linq.Linq3Implementation.Reflection;
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namespace MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MethodTranslators
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{
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internal static class DefaultIfEmptyMethodToAggregationExpressionTranslator
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{
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public static AggregationExpression Translate(TranslationContext context, MethodCallExpression expression)
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{
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var method = expression.Method;
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var arguments = expression.Arguments;
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if (method.IsOneOf(EnumerableMethod.DefaultIfEmpty, EnumerableMethod.DefaultIfEmptyWithDefaultValue))
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{
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var sourceExpression = arguments[0];
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var sourceTranslation = ExpressionToAggregationExpressionTranslator.Translate(context, sourceExpression);
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var sourceVar = AstExpression.Var("source");
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var sourceVarBinding = AstExpression.VarBinding(sourceVar, sourceTranslation.Ast);
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AstExpression defaultValueAst;
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if (method.Is(EnumerableMethod.DefaultIfEmpty))
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{
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var sourceItemSerializer = ArraySerializerHelper.GetItemSerializer(sourceTranslation.Serializer);
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var defaultValue = Activator.CreateInstance(sourceItemSerializer.ValueType);
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var serializedDefaultValue = SerializationHelper.SerializeValue(sourceItemSerializer, defaultValue);
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defaultValueAst = AstExpression.Constant(new BsonArray { serializedDefaultValue });
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}
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else
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{
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var defaultValueExpression = arguments[1];
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var defaultValueTranslation = ExpressionToAggregationExpressionTranslator.Translate(context, defaultValueExpression);
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defaultValueAst = AstExpression.ComputedArray(new[] { defaultValueTranslation.Ast });
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}
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var ast = AstExpression.Let(
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sourceVarBinding,
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AstExpression.Cond(
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AstExpression.Eq(AstExpression.Size(sourceVar), 0),
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defaultValueAst,
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sourceVar));
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return new AggregationExpression(expression, ast, sourceTranslation.Serializer);
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}
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throw new ExpressionNotSupportedException(expression);
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}
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}
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}

‎src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/SelectManyMethodToPipelineTranslator.cs

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@@ -135,8 +135,9 @@ private static AstPipeline TranslateSelectManyWithCollectionSelectorAndNonIdenti
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var collectionItemSerializer = ArraySerializerHelper.GetItemSerializer(collectionSelectorTranslation.Serializer);
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var resultSelectorSourceParameterExpression = resultSelectorLambda.Parameters[0];
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var resultSelectorSourceAst = AstExpression.Var("ROOT", isCurrent: true);
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var resultSelectorSourceParameterSymbol = context.CreateSymbol(resultSelectorSourceParameterExpression, resultSelectorSourceAst, sourceSerializer, isCurrent: true);
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var resultSelectorCollectionItemParameterExpression = resultSelectorLambda.Parameters[1];
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var resultSelectorSourceParameterSymbol = context.CreateSymbol(resultSelectorSourceParameterExpression, sourceSerializer, isCurrent: true);
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var resultSelectorCollectionItemParameterSymbol = context.CreateSymbol(resultSelectorCollectionItemParameterExpression, collectionItemSerializer);
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var resultSelectorContext = context.WithSymbols(resultSelectorSourceParameterSymbol, resultSelectorCollectionItemParameterSymbol);
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var resultSelectorTranslation = ExpressionToAggregationExpressionTranslator.Translate(resultSelectorContext, resultSelectorLambda.Body);

‎tests/MongoDB.Driver.Tests/Linq/Linq3ImplementationTests/Jira/CSharp3713Tests.cs

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/* Copyright 2010-present MongoDB Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System.Linq;
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using FluentAssertions;
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using Xunit;
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namespace MongoDB.Driver.Tests.Linq.Linq3ImplementationTests.Jira
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{
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public class CSharp3713Tests
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{
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[Fact]
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public void DefaultIfEmpty_should_work()
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{
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var client = DriverTestConfiguration.Linq3Client;
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var database = client.GetDatabase(DriverTestConfiguration.DatabaseNamespace.DatabaseName);
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var collection = database.GetCollection<C>(DriverTestConfiguration.CollectionNamespace.CollectionName);
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var subject = collection.AsQueryable();
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database.DropCollection(collection.CollectionNamespace.CollectionName);
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collection.InsertMany(new[] {
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new C { Id = 1, InnerArray = new A[0] },
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new C { Id = 2, InnerArray = new[] { new A { S = "abc" } } }
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});
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var queryable = subject.SelectMany(outerObject => outerObject.InnerArray.DefaultIfEmpty(), (o, a) => new { o, a });
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var stages = Linq3TestHelpers.Translate(collection, queryable);
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var expectedStages = new[]
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{
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"{ $project : { _v : { $map : { input : { $let : { vars : { source : '$InnerArray' }, in : { $cond : { if : { $eq : [{ $size : '$$source' }, 0] }, then : [{ S : null }], else : '$$source' } } } }, as : 'a', in : { o : '$$ROOT', a : '$$a' } } }, _id : 0 } }",
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"{ $unwind : '$_v' }"
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};
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Linq3TestHelpers.AssertStages(stages, expectedStages);
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var result = queryable.ToList();
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result.Count.Should().Be(2);
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result[0].o.Id.Should().Be(1);
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result[0].a.S.Should().Be(null);
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result[1].o.Id.Should().Be(2);
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result[1].a.S.Should().Be("abc");
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}
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[Fact]
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public void DefaultIfEmpty_with_explicit_default_should_work()
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{
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var client = DriverTestConfiguration.Linq3Client;
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var database = client.GetDatabase(DriverTestConfiguration.DatabaseNamespace.DatabaseName);
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var collection = database.GetCollection<C>(DriverTestConfiguration.CollectionNamespace.CollectionName);
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var subject = collection.AsQueryable();
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database.DropCollection(collection.CollectionNamespace.CollectionName);
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collection.InsertMany(new[] {
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new C { Id = 1, InnerArray = new A[0] },
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new C { Id = 2, InnerArray = new[] { new A { S = "abc" } } }
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});
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var defaultValue = new A { S = "default" };
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var queryable = subject.SelectMany(outerObject => outerObject.InnerArray.DefaultIfEmpty(defaultValue), (o, a) => new { o, a });
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var stages = Linq3TestHelpers.Translate(collection, queryable);
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var expectedStages = new[]
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{
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"{ $project : { _v : { $map : { input : { $let : { vars : { source : '$InnerArray' }, in : { $cond : { if : { $eq : [{ $size : '$$source' }, 0] }, then : [{ S : 'default' }], else : '$$source' } } } }, as : 'a', in : { o : '$$ROOT', a : '$$a' } } }, _id : 0 } }",
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"{ $unwind : '$_v' }"
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};
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Linq3TestHelpers.AssertStages(stages, expectedStages);
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var result = queryable.ToList();
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result.Count.Should().Be(2);
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result[0].o.Id.Should().Be(1);
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result[0].a.S.Should().Be("default");
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result[1].o.Id.Should().Be(2);
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result[1].a.S.Should().Be("abc");
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}
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private class C
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{
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public int Id { get; set; }
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public A[] InnerArray { get; set; }
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}
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private class A
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{
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public string S { get; set; }
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}
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}
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}

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