Translating SQL CASE Statements to LINQ: A Practical Guide
This article addresses the challenge of converting SQL CASE statements into their LINQ equivalents. A user sought assistance in translating the following SQL snippet:
osc_products.products_quantity = CASE WHEN itempromoflag 'N' THEN 100000 WHEN itemcat1 IN ('1','2','31') AND itemsalestatus = 'S' THEN 100000 WHEN itemsalestatus = 'O' THEN 0 ELSE cds_oeinvitem.itemqtyonhand - cds_oeinvitem.itemqtycommitted END
The initial LINQ attempt provided was insufficient:
cdsDBDataContext db = new cdsDBDataContext(); var query = from items in db.cdsItems where items.ItemHandHeldFlag.Equals("Y") && items.ItemQtyOnHand - items.ItemQtyCommitted > 0 select items;
This query only filters data; it doesn't implement the logic of the SQL CASE statement.
For a clearer illustration of LINQ's CASE statement equivalent, let's examine a simpler example:
Int32[] numbers = new Int32[] { 1, 2, 1, 3, 1, 5, 3, 1 }; var numberText = ( from n in numbers where n > 0 select new { Number = n, Text = ( n == 1 ? "One" : n == 2 ? "Two" : n == 3 ? "Three" : "Unknown" ) } );
This demonstrates the use of the ternary conditional operator (?:
) to mimic the behavior of a CASE statement. The conditions are evaluated sequentially, returning the appropriate value for each match. The result is a sequence of anonymous objects, each containing a number and its textual representation. Applying this principle to the original SQL CASE statement requires a similar nested conditional approach within the LINQ query, adapting it to the specific data structure and relationships within db.cdsItems
and potentially joining with other tables to access itempromoflag
, itemcat1
, and itemsalestatus
. The ELSE
condition would represent the default value if none of the preceding conditions are met.
The above is the detailed content of How Can I Effectively Translate SQL CASE Statements into LINQ Queries?. For more information, please follow other related articles on the PHP Chinese website!

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