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  1. C# Driver
  2. CSHARP-4542

LINQ3 support for projecting to a ValueTuple<>

    • Type: Icon: Bug Bug
    • Resolution: Duplicate
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 2.19.0
    • Component/s: LINQ3
    • None
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      1. What would you like to communicate to the user about this feature?
      2. Would you like the user to see examples of the syntax and/or executable code and its output?
      3. Which versions of the driver/connector does this apply to?

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      1. What would you like to communicate to the user about this feature? 2. Would you like the user to see examples of the syntax and/or executable code and its output? 3. Which versions of the driver/connector does this apply to?

      the following code results in an expression not supported exception in LINQ3 while it used to work with LINQ2:

      var result = await personQueryable
          .Select(p => new ValueTuple<string, string>(p.FirstName, p.LastName))
          .ToListAsync(); 

      stack trace:

      MongoDB.Driver.Linq.ExpressionNotSupportedException
        HResult=0x80131515
        Message=Expression not supported: new ValueTuple`2(p.FirstName, p.LastName) because constructor parameter item1 does not match any property.
        Source=MongoDB.Driver
        StackTrace:
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.NewExpressionToAggregationExpressionTranslator.GetMatchingPropertyName(NewExpression expression, String constructorParameterName)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.NewExpressionToAggregationExpressionTranslator.<>c__DisplayClass0_0.<Translate>b__1(ParameterInfo p)
         at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.NewExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, NewExpression expression)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, Expression expression)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(TranslationContext context, LambdaExpression lambdaExpression, IBsonSerializer parameterSerializer, Boolean asRoot)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators.SelectMethodToPipelineTranslator.Translate(TranslationContext context, MethodCallExpression expression)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators.ExpressionToPipelineTranslator.Translate(TranslationContext context, Expression expression)
         at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToExecutableQueryTranslators.ExpressionToExecutableQueryTranslator.Translate[TDocument,TOutput](MongoQueryProvider`1 provider, Expression expression)
         at MongoDB.Driver.Linq.Linq3Implementation.MongoQuery`2.ToCursorAsync(CancellationToken cancellationToken)
         at MongoDB.Driver.IAsyncCursorSourceExtensions.<ToListAsync>d__16`1.MoveNext()

      however projecting to a Tuple<> works just fine.

            Assignee:
            robert@mongodb.com Robert Stam
            Reporter:
            djnitehawk83@gmail.com Damith G
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              Created:
              Updated:
              Resolved: