C# 4 and .NET 4

Commands ❘ 831
This command accepts only a single parameter, as shown in the following code, which will execute the
RegionDelete stored procedure; here, you see an example of setting the parameter by name. If you have
many similar calls to make to the same stored procedure, constructing SqlParameter instances and
setting the values as in the following code may lead to better performance than reconstructing the entire
SqlCommand for each call.
cmd.Parameters["@RegionID"].Value= 999;
cmd.ExecuteNonQuery();
Calling a stored Procedure That returns output Parameters
Both of the previous examples execute stored procedures that return nothing. If a stored procedure
includes output parameters, these need to be defined within the .NET client so that they can be filled
when the procedure returns. The following example shows how to insert a record into the database and
return the primary key of that record to the caller.
Record Insertion
The Region table consists of only a primary key (RegionID) and description field (RegionDescription). To
insert a record, this numeric primary key must be generated, and then a new row needs to be inserted into
the database. The primary key generation in this example has been simplified by creating one within the
stored procedure. The method used is exceedingly crude, which is why there is a section on key generation
later in this chapter. For now, this primitive example suffices:
CREATE PROCEDURE RegionInsert(@RegionDescription NCHAR(50),
@RegionID INTEGER OUTPUT)AS
SET NOCOUNT OFF
SELECT @RegionID = MAX(RegionID)+ 1
FROM Region
INSERT INTO Region(RegionID, RegionDescription)
VALUES(@RegionID, @RegionDescription)
GO
code download StoredProcs.sql
The insert procedure creates a new Region record. Because the primary key value is generated by the
database itself, this value is returned as an output parameter from the procedure (@RegionID). This is
sufficient for this simple example, but for a more complex table (especially one with default values), it
is more common not to use output parameters, and instead select the entire inserted row and return this
to the caller. The .NET classes can cope with either scenario.
SqlCommand cmd = new SqlCommand("RegionInsert", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new SqlParameter("@RegionDescription",
SqlDbType.NChar,
50,
"RegionDescription"));
cmd.Parameters.Add(new SqlParameter("@RegionID",
SqlDbType.Int,
0,
ParameterDirection.Output,
false,
0,
0,
"RegionID",
DataRowVersion.Default,
null));
cmd.UpdatedRowSource = UpdateRowSource.OutputParameters;
code download StoredProcs.cs
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