How to Implement a SQL CASE Statement Equivalent in LINQ for Conditional Product Quantity Assignment?

Replicating SQL CASE Statements in LINQ for Dynamic Product Quantity Allocation

This article demonstrates how to translate the functionality of a SQL CASE statement into LINQ, specifically addressing the challenge of conditionally assigning product quantities based on various criteria. We'll modify existing code to incorporate this logic.

The initial calculation:

<code class="language-csharp">cds_oeinvitem.itemqtyonhand - cds_oeinvitem.itemqtycommitted</code>

This simple subtraction determines available inventory by deducting committed quantities from the on-hand stock.

The SQL CASE statement equivalent in LINQ uses nested ternary operators:

<code class="language-csharp">osc_products.products_quantity =
    itempromoflag != "N" ? 100000 :
    (
        itemcat1.In("1", "2", "31") && itemsalestatus == "S" ? 100000 :
        itemsalestatus == "O" ? 0 :
        cds_oeinvitem.itemqtyonhand - cds_oeinvitem.itemqtycommitted
    )</code>

This nested structure mirrors the conditional logic of a CASE statement. It prioritizes conditions: if itempromoflag is not "N", the quantity is 100000; otherwise, it proceeds to the next condition, and so on.

The integrated LINQ query:

<code class="language-csharp">cdsDBDataContext db = new cdsDBDataContext();
var query = from items in db.cdsItems
            where items.ItemHandHeldFlag == "Y" &&
                  (
                      items.Itempromoflag != "N" ? 100000 :
                      (
                          items.Itemcat1.In("1", "2", "31") && items.Itemsalestatus == "S" ? 100000 :
                          items.Itemsalestatus == "O" ? 0 :
                          items.Itemqtyonhand - items.Itemqtycommitted
                      )
                  ) > 0
            select items;</code>

This revised query incorporates the conditional quantity assignment, ensuring that stock status is accurately updated based on the defined criteria. Only items meeting the ItemHandHeldFlag condition and having a resulting quantity greater than zero are selected. This effectively replicates the behavior of a SQL CASE statement within the LINQ framework.

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