DeriveParameters Method

Retrieves parameter information from the Advanced SQL Engine and populates the Parameters collection of the passed in TdCommand object.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Shared Sub DeriveParameters( _
   ByVal command As TdCommand _
)

'Usage
 
Dim command As TdCommand
 
TdCommandBuilder.DeriveParameters(command)

public static void DeriveParameters( 
   TdCommand command
)

public:
static void DeriveParameters( 
   TdCommand^ command
)

Parameters

command: The TdCommand object to derive parameters.

Exceptions

Exception	Description
System.InvalidOperationException	CommandType property of the command object is not set to Data.CommandType.StoredProcedure or Data.CommandType.Text.
TdException	The Advanced SQL Engine generated an error.

Remarks

The Data Provider will send a HELP PROCEDURE statement to retrieve the stored procedure parameter information from the Advanced SQL Engine when TdCommand.CommandType is set to StoredProcedure and TdCommand.CommandText is a Stored Procedure name. The information is used to populate the command. The parameters collection is populated with TdParameter objects, one for each stored procedure parameter. TdParameter Direction, IsNullable, ParameterName, Precision, Scale, Size and TdType properties will be set.

When the TdParameter.TdType property is set as a TdType.AnyType, the Precision, Scale and Size are not available. The TdType.AnyType indicates that the actual TdType and value will be supplied during execution of the stored procedure, enabling selection of a dynamic TdType to the stored procedure.

When OUT parameter types are defined as TdType.AnyType, the parameter information ordinarily supplied by the HELP PROCEDURE statement must be supplied in the parameter collection by the program. TdParameter.SecondaryTdType must be defined to indicate the actual TdType supplied during execution of the stored procedure. The Precision, Scale, Size and Value must also be supplied additionally if applicable.

The Data Provider will Prepare the command when TdCommand.CommandType is set to Text. The TdCommand.Parameters properties is populated from the Metadata. CommandType.Text must not be used with CALL statements.

Example

The following example illustrates setting up a parameter collection, given the following definition of an external stored procedure:

REPLACE PROCEDURE xspAnyType02(IN param2 INTEGER, OUT result2 TD_ANYTYPE)

public static void DeriveTdAnyTypeParameters(TdCommand myCommand) 
{
    myCommand.CommandType = CommandType.StoredProcedure;
    TdCommandBuilder.DeriveParameters(myCommand);
    
    Debug.Assert(2 == myCommand.Parameters.Count);
    Debug.Assert(ParameterDirection.Input == myCommand.Parameters[0].Direction);
    Debug.Assert(TdType.Integer == myCommand.Parameters[0].TdType);
    Debug.Assert(ParameterDirection.Output == myCommand.Parameters[1].Direction);
    Debug.Assert(TdType.AnyType == myCommand.Parameters[1].TdType);
            
    myCommand.Parameters[0].Value = 20;
            
    myCommand.Parameters[1].SecondaryTdType = TdType.VarChar;
    myCommand.Parameters[1].Size = 20;
    
    myCommand.ExecuteReader();
    Console.WriteLine("Result is {0}", myCommand.Parameters[1].Value);
}

Requirements

Target Platforms: Windows 8.1, Windows 10, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019

Reference

TdCommandBuilder Class
TdCommandBuilder Members