What is ExecuteScalar in ADO.NET and when should you use it?

ExecuteScalar is used to retrieve a single value from the database, typically the first column of the first row in the result set.

Purpose: Designed for queries that return a single value (e.g., COUNT, SUM, MAX) Performance: More efficient than ExecuteReader when only one value is needed Behavior: Ignores remaining rows/columns after the first value Common Use Cases: Getting record counts Fetching identity values Comparison: ExecuteReader → multiple rows ExecuteNonQuery → no return value ExecuteScalar → single value