How to Perform an Inner Join with an ON Clause Using LINQ to SQL?

Using LINQ to SQL for Efficient Inner Joins with ON Clause

LINQ to SQL offers a streamlined approach to executing SQL queries within C#. A frequent requirement is the inner join, merging data from multiple tables based on a matching condition.

LINQ to SQL Syntax:

The structure for an inner join utilizing an ON clause in LINQ to SQL is as follows:

<code class="language-csharp">from t1 in db.Table1
join t2 in db.Table2 on t1.field equals t2.field</code>

Illustrative Example:

Consider this SQL query:

<code class="language-sql">select DealerContact.*
from Dealer
inner join DealerContact on Dealer.DealerID = DealerContact.DealerID</code>

Equivalent LINQ to SQL Query:

<code class="language-csharp">var dealercontacts = from contact in db.DealerContact
                     join dealer in db.Dealer on contact.DealerId equals dealer.Id
                     select contact;</code>

This LINQ query achieves the same result:

• dealercontacts stores the query's output.
• db.DealerContact references the first table.
• db.Dealer references the second table.
• contact.DealerId and dealer.Id are the join keys.

Important Consideration:

It's crucial to verify that the table and field names in your LINQ query precisely align with your database schema. Any discrepancies will lead to errors.

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