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POLINQ getting the latest entries
 

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  1. POLINQ getting the latest entries
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    <p>I'm fairly new to LINQ, so this might be an easy peasy solution for some of you. I've been ripping my hair out for quite a while now :)</p> <p>Scenario: I have a box containing 3 Hardware Modules that have diffrent ports. Using Serial comunication I extract data from the modules into a SQL table called CurrentData_Tables So each time a unit gets produced, my program will write an entry into the table saying how big the sum is. Let me try and explain the data.</p> <pre><code>BoxID, ModuleID, PortNumber, Value, Time 1, 0A, 1, {Value}, {Date} </code></pre> <p>The time is excatly the same on the readings for that specific module, so I imagined I could group by the data that is constant and then just get the latest. This is what I have so far:</p> <pre><code>SQLdbDataContext sqlDB = new SQLdbDataContext(); BindingSource bs = new BindingSource(); var Latest = from q in sqlDB.CurrentData_Tabels group q by new { q.BoxID, q.ModuleID, q.PortNumber, q.Time } into groupOrder select new { BoxID = groupOrder.Key.BoxID, ModuleID = groupOrder.Key.ModuleID, Portnumber = groupOrder.Key.PortNumber, Time = groupOrder.Key.Time }; </code></pre> <p>And that's perfectly fine because I get all the results I want and more. I don't need to know that the reading on module 0A, port 1 had counted to 2 before the latest entry of 3. Does that make sense? If not please let me try to explain it again.</p> <p>Doing a > to get the largest sum wouldn't work since I also have statuses that trigger on bool values. One means there's an alarm present on the machine and zero means all is OK.</p> <p>I'm sorry for the double post. For whatever reason my temporary account was locked out and I couldn't comment on my old post. Now I'm registered and should hopefully be able to provide additional information.</p> <p>@Jon Skeet, Here's the setup with 2 active ports on Module 0B, Imagine that there had been an alarm active on module 0B port 1, then i would still get the outdated data shown even though the problem had been resolved.</p> <p><a href="http://i.stack.imgur.com/oX1ZK.jpg" rel="nofollow">http://i.stack.imgur.com/oX1ZK.jpg</a></p> <p>Here's how it would look at my client side:</p> <p><a href="http://i.stack.imgur.com/stBXY.jpg" rel="nofollow">http://i.stack.imgur.com/stBXY.jpg</a></p> <p>Obviously i would only like to display the latest Data. I hope this clears up the confusion.</p> <hr> <p>I seem to have resolved my own issue but in a nonefficient way.</p> <pre><code>SQLdbDataContext sqlDB = new SQLdbDataContext(); var LatestObjects = (from q in sqlDB.CurrentData_Tabels select q).OrderByDescending(x =&gt; x.Time).First(); var selectedobjects = from q in sqlDB.CurrentData_Tabels where q.Time == LatestObjects.Time select q; dgvLiveData.DataSource = selectedobjects; dgvLiveData.RowHeadersVisible = false; </code></pre> <p>By combining 2 queries I got what I wanted. I'm sure this could be resolved using one query but I'm nowhere near being a hardcore programmer that would figure that one out.</p>
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    1. USjlafay
    1. USSimon Lausten
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      1. POLINQ getting the latest entries
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    1. COFrom what I can see `LatestObjects` already have what you want, the other query doesn't do anything more.
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      1. USMagnus
    2. COThe top one wouldn't return anything magnus :), it's only there to turn the table upside down and get the latest time entry.
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      1. POLINQ getting the latest entries
      1. USSimon Lausten
 

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