DirectionalQueryField

A query field that supports bidirectional parameter passing (input/output) via the ParamDirection enumeration in System.Data. It extends QueryField with the ability to receive output values from the database after execution.

This is useful for calling stored procedures that return output parameters.

Given the following stored procedure:

CREATE PROCEDURE [dbo].[sp_Multiply]
(
    @Value1 DOUBLE
    , @Value2 DOUBLE
    , @Output DOUBLE OUT
)
AS
BEGIN
    SET @Output = @Value1 * @Value2;
END

Call it as follows:

using (var connection = new SqlConnection(connectionString))
{
    var output = new DirectionalQueryField("Output", typeof(double), ParamDirection.Output);
    var param = new []
    {
        new QueryField("Value1", 100),
        new QueryField("Value2", 200),
        output
    };
    var result = connection.ExecuteNonQuery("sp_Multiply", param, commandType: CommandType.StoredProcedure);
    // Use the 'output' here like below
    var value = output.GetValue<double>(); // Or, you can also access the parameter itself like `output.Parameter.Value`
}

The second constructor argument specifies the .NET CLR type of the database parameter. For input/output parameters, pass the value directly — the library infers the type from the value.

var output = new DirectionalQueryField("Output", "Whatever", 256, ParamDirection.InputOutput); // Type is TEXT
var output = new DirectionalQueryField("Output", 100, ParamDirection.InputOutput); // Type is INT

When using ExecuteReader, output parameter values are only populated after the DbDataReader is disposed. This is standard ADO.NET behavior.

For more information, see the base class QueryField.