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POLinq Query To Combine 2 Lists
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  1. POLinq Query To Combine 2 Lists
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    copied!<p>I have 2 lists and I need to combine the joining values from A and B, but also include the values from A and B that don't match the join.</p> <pre><code>class TypeA { public string Key { get; set; } public int ValueA { get; set; } } class TypeB { public string Key { get; set; } public int ValueB { get; set; } } class TypeAB { public string Key { get; set; } public int ValueA { get; set; } public int ValueB { get; set; } } var listA = new List&lt;TypeA&gt; { new TypeA { Key = "one", Value = 1 }, new TypeA { Key = "two", Value = 2 }, }; var listB = new List&lt;TypeB&gt; { new TypeB { Key = "two", Value = 2 }, new TypeB { Key = "three", Value = 3 }, }; </code></pre> <p>I want these lists combined to equal this:</p> <pre><code>var listAB = new List&lt;TypeAB&gt; { new TypeAB { Key = "one", ValueA = 1, ValueB = null }, new TypeAB { Key = "two", ValueA = 2, ValueB = 2 }, new TypeAB { Key = "three", ValueA = null, ValueB = 3 }, }; </code></pre> <p>What is a Linq statement that will do this? I've been playing around and can't quite get there. I can get almost there by doing a left outer join on A to B and Union that to a left outer join on B to A, but I get duplicate Intersection values.</p> <p><strong>Update</strong></p> <p>Here is what I did based on George's answer:</p> <pre><code>var joined = ( from a in listA join b in listB on a.Key equals b.Key into listBJoin from b in listBJoin.DefaultIfEmpty( new TypeB() ) select new TypeAB { Key = a.Key, ValueA = a.ValueA, ValueB = b.ValueB, } ).Union( from b in listB where !listA.Any( d =&gt; d.Key == b.Key ) select new TypeAB { Key = b.Key, ValueB = b.ValueB, } ).ToList(); </code></pre>
 

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