Outputparameter

OutputParameter refers to a parameter in a function or procedure that is used to return data to the caller in addition to the method’s primary return value. It is passed by reference and assigned within the method, enabling multiple values to be returned without relying on a separate return object. Output parameters are commonly used when a single return value is insufficient or when related results must be produced together.

In programming languages such as C# and VB.NET, output parameters are implemented as out/ref (C#) or ByRef (VB). Output parameters declared with out must be assigned inside the method and are considered uninitialized on entry. In SQL and stored procedures, parameters can be defined as OUTPUT so the procedure writes the value that the caller can retrieve after execution.

Typical use cases include returning computed statistics, counts, or complex results that are best represented as separate values, such as reporting both a data payload and its size, or signaling a status alongside data. They are also used when the language or API design favors returning multiple values without creating a composite object.

Design considerations include API clarity and ease of use. Overreliance on output parameters can reduce readability and introduce fragility due to parameter mutation and ordering requirements. When possible, returning a single composite object or a tuple can improve clarity. Always initialize output parameters appropriately and handle error conditions to avoid leaving them with undefined values.

Example (conceptual): a function GetStats(data, out int count, out double average) computes count and average of data and assigns them to the output parameters, allowing the caller to read both results after the call.