Reading and setting the declaration and implementation of a POU

Each POU with a declaration and implementation area exposes these via the interfaces ITcPlcDeclaration and ITcPlcImplementation. You can read and set both areas using the properties DeclarationText and ImplementationText. ImplementationXml provides the implementation in PLCopen XML format.

Requirements

TwinCAT XAE is installed and started.
A DTE connection to the target instance is active.
ITcSysManager is initialized in an STA thread.
The target POU is included in the PLC project.

Setting the declaration and implementation

The POU's Tree Item is converted via cast to ITcPlcDeclaration and ITcPlcImplementation. The respective content is set using the properties DeclarationText and ImplementationText.

// Cast directly to declaration and implementation interfaces
ITcSmTreeItem method = sysManager.LookupTreeItem(@"TIPC^PLC1^PLC1 Project^POUs^MyFB^MyMethod");
ITcPlcDeclaration decl = method as ITcPlcDeclaration;
decl.DeclarationText = "VAR_INPUT\n    nValue : INT;\nEND_VAR";

ITcPlcImplementation impl = method as ITcPlcImplementation;
impl.ImplementationText = "MyMethod := nValue > 0;";

Reading the declaration and implementation

These same properties can also be read. The following sample creates a function block and then reads its declaration, implementation, and implementation XML.

$plcPousItem = $systemManager.LookupTreeItem("TIPC^PlcGenerated^PlcGenerated Project^POUs")
$newFb = $plcPousItem.CreateChild("FB_TEST", 604, "", 6)

$decl = $newFb.DeclarationText
$impl = $newFb.ImplementationText
$implXml = $newFb.ImplementationXml

POU types with declaration and implementation areas

Not every type of POU has both areas. The following table shows which types have a declaration area and which have an implementation area.

Tree Item	Type	Declaration area	Implementation area
Program	POU	Yes	Yes
Function	POU	Yes	Yes
Function block	POU	Yes	Yes
Action	POU	No	Yes
Method	POU	Yes	Yes
Property (Get/Set)	POU	Yes	Yes
Transition	POU	No	Yes
Enum	DUT	Yes	No
Struct	DUT	Yes	No
Union	DUT	Yes	No
Alias	DUT	Yes	No
Interface	Interface	Yes	No
Property (Get/Set)	Interface	Yes	Yes
Global variables	GVL	Yes	No

	The process of creating POUs and other PLC objects is described in Creating PLC objects.