UserStruct.md

User Struct

(FBWithUserStruct.cs)

To make a structure visible in PLCnext Engineer, the attribute [Structure] is needed and the fields must be declared public.

    [Structure]
    public struct Position
    {
        public int x;
        public int y;
    }

Using the structure in your C# code can be used as Input and Output as well.

    [FunctionBlock]
    public class FB_with_user_struct
    {
        [Input]
        public Position NEW_POSITION;

For larger structs it could be interesting to pass it by reference. Not buffering the values saves memory and CPU time. This works only for InOut parameters. The field and the execution method needs the unsafe modifier. This denotes an unsafe code, which is required for any operation involving pointers.

Note:

• unsafe code is only possible if in project Properties Build settings "Allow unsafe code" is switched on.
• The use of pointer is currently only supported by InOut parameter.

[InOut]
unsafe public Position* NEW_POSITION;
...
[Execution]
unsafe public void __Process()
{
    if ((CURRENT_POSITION).x < (*NEW_POSITION).x)
    {
       ...

Two function block variants are implemented

Both function blocks are called with an input and output structure. The output structure is modified in dependency of the input structure.

1. FunctionBlock1
   Implements the function block with parameter passing by value
2. FunctionBlock2
   Implements the function block with parameter passing by reference which means [InOut] parameter declaration is used.