Stored procedures

Call a procedure by name with ProcedureParameters. The command runs with CommandType.StoredProcedure, so the provider builds the call syntax.

var parameters = new ProcedureParameters()
    .Add("customer_id", 42)
    .Output<decimal>("balance")
    .InputOutput("attempts", 0);
 
await db.ExecuteProcedureAsync("get_balance", parameters);
 
decimal balance = parameters.Get<decimal>("balance");
int attempts = parameters.Get<int>("attempts");

Method	Adds
`Add(name, value)`	an input parameter
`Output<T>(name, size?)`	an output parameter; strings and byte arrays default to the maximum size
`InputOutput<T>(name, value, size?)`	a parameter that passes a value in and receives one back
`ReturnValue(name = "ReturnValue")`	the procedure's `RETURN` value (SQL Server)

Give names without a prefix. MicroORM adds the one the provider expects (@name for SQL Server and MySQL, a bare name for PostgreSQL).

Some providers write the procedure and parameter names into the generated CALL text, so MicroORM only accepts identifiers: a procedure name is one to four dot-separated parts (billing.get_balance), each bare or quoted the dialect's way ("odd name", [odd name], `odd name`), and a parameter name uses letters, digits, _ and $. Anything else throws ArgumentException. Never build either from user input.

Procedures that return rows

var parameters = new ProcedureParameters().Add("min_age", 30).Output<int>("total_count");
var people = await db.QueryProcedureAsync<Person>("people_older_than", parameters);
int total = parameters.Get<int>("total_count");   // outputs are available once the rows are read

Synchronous calls

ExecuteProcedure and QueryProcedure<T> are the synchronous forms.

Per database

Database	Notes
SQL Server	Inputs, outputs, input/outputs, return values and result sets.
MySQL / MariaDB	`IN`, `OUT` and `INOUT` parameters and result sets.
PostgreSQL	Procedures (`CALL`) with `OUT` and `INOUT` parameters. PostgreSQL procedures can't return rows: for a function that returns a table, use `db.QueryAsync<T>($"SELECT * FROM fn({arg})")`.
SQLite	No stored procedures; calls throw `NotSupportedException`.

A ProcedureParameters instance holds the results of its most recent call. Use a new instance for each call, and don't share one between concurrent calls.