How to Perform Left Outer Joins in LINQ without `join-on-equals-into` Clauses?

No need to perform the left external connection

join-on-equals-into In C# Linq to Objects, you can use the

method to execute the left external connection of the

clause. DefaultIfEmpty() join-on-equals-into Solution on the left external connection

To use the clause to execute the left external connection, please modify the code as follows:

Explanation Where

<code class="language-csharp">List<joinpair> leftFinal = (from l in lefts
                             join r in rights on l.Key equals r.Key into temp
                             from r in temp.DefaultIfEmpty()
                             select new JoinPair { LeftId = l.Id, RightId = r == null ? 0 : r.Id });</code>

If the connection conditions do not match, return the default value of the collection type that is connected (

in this example). This ensures that all the lines in the left table () are included in the results, even if there is no matching line in the right table ().

Example

DefaultIfEmpty() JoinPair Considering the code provided for internal connection: lefts rights

To achieve the left external connection, please replace

clauses into the following:

This modification will ensure that all the lines in the left

are included in the results, including those lines that are not matched in the right

.

<code class="language-csharp">List<joinpair> innerFinal = (from l in lefts
                             from r in rights
                             where l.Key == r.Key
                             select new JoinPair { LeftId = l.Id, RightId = r.Id });</code>

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