How to Use Dapper ORM's IN Clause with Dynamically Generated Lists?

Querying with IN Clause and Dapper ORM

Question:

How to efficiently construct an SQL query with an IN clause using Dapper ORM when the list of values for the IN clause is dynamically derived from business logic?

Answer:

Dapper ORM provides direct support for this scenario. Here's how to do it:

string sql = "SELECT * FROM SomeTable WHERE id IN @ids";
var results = conn.Query(sql, new { ids = new[] { 1, 2, 3, 4, 5 }});

In this example, the ids parameter is defined as an array of integers. The comma-separated list of IDs in the original query is dynamically constructed based on business logic and passed as the value for the ids parameter.

If you are using Postgres as the database, a slight modification is required to properly handle arrays within the IN clause:

// Define a custom type to represent an array of integers
var postgresIntArray = new PostgresIntArray { Value = new[] { 1, 2, 3, 4, 5 } };

string sql = "SELECT * FROM SomeTable WHERE id IN @ids";
var results = conn.Query(sql, new { ids = postgresIntArray});

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