Generated code - Calling a stored procedure, Adapter
Preface
LLBLGen Pro supports stored procedures by offering the ability to define
calls to those stored procedures.
There are two types of stored procedures: procedures which do not return a resultset, called
Action Stored Procedures, and
procedures which return one or more resultsets, which are called
Retrieval
Stored Procedures. This section illustrates how call definitions to these
stored procedures in your project are generated in code and how you can use
them in your code. Classes with stored procedure calls are stored in the
database specific VS.NET project.
To fetch a
TypedView
mapped onto a resultset of a stored procedure please see
using the TypedView classes, Adapter.
Retrieval Stored Procedure Calls
When you add a call definition for a retrieval stored procedure
to the project in the LLBLGen Pro designer, a static/shared method that will call that stored
procedure will be added to a class called
RetrievalProcedures. If the stored procedure returns a single resultset, the return value of the generated method will be a
DataTable. When the stored procedure returns more than one resultset, the return value of the
generated method will be a
DataSet, containing each resultset in a separate
DataTable.
For example, if we add a call definition to our LLBLGen Pro project to the procedure in Northwind
called
CustOrderDetail, taking one parameter, an OrderID, a static
method called
CustOrderDetail is created, returning a
DataTable
(because the procedure returns a single resultset) and accepting
a single parameter, orderID, which is of type int/Integer because the parameter itself is of type integer. To utilize
this method in your own code, you can call as shown below. For the orderID,
the value 10254 is passed as the parameter value:
// [C#]
DataTable resultSet = RetrievalProcedures.CustOrderDetail(10254);
' [VB.NET]
Dim resultSet As DataTable = RetrievalProcedures.CustOrderDetail(10254)
Because the stored procedure call methods are located in the database specific project, they will create a new
DataAccessAdapter object if not such an
object is supplied, which is the case in our example above. If you want to use an existing
DataAccessAdapter, for example because you want the
stored procedure to run inside an existing transaction, you can specify that existing adapter in the method call as an extra parameter.
Output parameters are also supported. When a stored procedure has an output parameter, a parameter representing the output
parameter in the stored procedure is added to the method heading and is defined as 'ref' (C#) or 'ByRef' (VB.NET). Illustrated
below is the call to an imaginary stored procedure which returns a datatable, takes 4 input parameters
and returns a value in an output parameter:
// [C#]
int outputValue;
DataTable resultSet = RetrievalProcedures.MyStoredProcedure(1, 2, 3, 4, ref outputValue);
' [VB.NET]
Dim outputValue as Integer
Dim resultSet As DataTable = RetrievalProcedures.MyStoredProcedure(1, 2, 3, 4, ByRef outputValue)
Action Stored Procedure Calls
If you have added a call to a procedure to your project and the stored
procedure doesn't return a resultset, the static/shared method is
added to the class
ActionProcedures. Instead of returning a
DataTable or
DataSet, a method in this class returns an int/Integer,
which represents the return value of the
ExecuteNonQuery() method, which is the number of rows affected if the database
has row counting enabled (and the stored procedure doesn't switch it off). Otherwise the action stored procedure methods
work the same as the retrieval stored procedures mentioned above: input parameters are defined as normal parameters for the
method and output parameters are defined as ref/ByRef parameters.
Wrap call in IRetrievalQuery object
LLBLGen Pro offers you to get the call to a retrieval stored procedure as an
IRetrievalQuery object. An
IRetrievalQuery object is the
query object generated by a Dynamic Query Engine (DQE) and which is executed by the low level fetch logic of LLBLGen Pro's O/R mapper core. The
IRetrievalQuery object allows you to fetch a query as a datareader or to project the results of the stored procedure call onto a data-structure of your choice, for example
an entity collection. You retrieve an
IRetrievalQuery object which wraps the call to a given stored procedure by calling the following generated
method (each retrieval stored procedure has such a method generated):
// C#
IRetrievalQuery procCall = RetrievalProcedures.GetStoredProcedureCallNameCallAsQuery(parameters);
' VB.NET
Dim procCall As IRetrievalQuery = RetrievalProcedures.GetStoredProcedureCallNameCallAsQuery(parameters)
You can then pass the
IRetrievalQuery object to the methods for fetching a datareader or fetch a projection. See for more information about fetching
a datareader or fetching a projection:
LLBLGen Pro - Fetching DataReaders and projections.