MongoDB Collections Join

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    • Type: New Feature
    • Resolution: Gone away
    • Priority: Major - P3
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    • Affects Version/s: None
    • Component/s: LINQ
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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?
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      Mongodb collection join using C# driver and LINQ. I found two relevant solutions list below
       

      var table1 = _myRepo.GetAll();
var table2 = table1.Where(x => x.Type == "MyType");
var try1 = 
    (
        from x in table1
        join y in table2 on new { a = x.ClaimId, b = x.CensusId } equals new { a = y.ClaimId, b = y.CensusId }
        select x
    )
    .ToList();

      This query will throw exception The Join query operator is not supported.
       

      var try2 = 
    (
        from x in table1
        from y in table2
        where x.ClaimId == y.ClaimId && x.CensusId == y.CensusId
        select x
    )
    .Select(x => x)
    .ToList();

      This query will throw exception The SelectMany query operator is not supported

      But below query works
       

      var table1 = _arRepository.GetAll();
var table2 = table1.Where(x => x.Type == "MyType");
var claimIds = table2.Select(x => x.ClaimId).Distinct().ToList();
var censusIds = table2.Select(x => x.CensusId).Distinct().ToList();
var data = table1.Where(x => claimIds.Contains(x.ClaimId) && censusIds.Contains(x.CensusId));

      The problem with this is that it loads the (claimIds and censusIds ) in memory, Actually I want to executes this on server so that it return only required data. I also found a blog for newly mongodb feature (Lookup) discussed in

      Blog: https://www.axonize.com/blog/iot-technology/joining-collections-in-mongodb-using-the-c-driver-and-linq/ I flow the blog to install required drivers
       

      <PackageReference Include="mongocsharpdriver" Version="2.9.2" />
<PackageReference Include="MongoDB.Bson" Version="2.9.2" />
<PackageReference Include="MongoDB.Driver" Version="2.9.2" />
<PackageReference Include="MongoDB.Driver.Core" Version="2.9.2" />

            Assignee:
            Robert Stam (Inactive)
            Reporter:
            Farooq Awan
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            0 Vote for this issue
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              Created:
              Updated:
              Resolved: