Modified S7StringAttribute support for Class Type.

[Jason-Jelks]

Classes can now include String properties by adding the "S7StringAttribute" to the Properties to define maximum string size. The Attribute is required for Class type implementing a String.

Classes can now include DateTime Properties. The internal call structures now support passing the current CPU instantiated so that the proper DateTime structure is implemented based on the PLC.
S7-1200 & S71500 : use DateTimeLong (DTL - 12-bytes)
all others use: older DT 8-byte format as they don't support the DTL
The CPU parameter does not break existing implementations, but does default direct calls made by an external source to S7-300 if not defined.

[dhullett08]

I tried using the new string functionality for classes and it wouldn't work. It works perfectly for structs but I had to change from using the underlying type of the property to propertyinfo to be able to get the S7StringAttribute as well as increment numBytes with the ReservedLengthInBytes property.

// new get property value
private static object? GetPropertyValue(PropertyInfo property, byte[] bytes, ref double numBytes, CpuType cpu) `

// getting attribute from instance not type and increment numBytes
S7StringAttribute? attribute = property.GetCustomAttributes().SingleOrDefault();

if (attribute == default(S7StringAttribute))
throw new ArgumentException("Please add S7StringAttribute to the string property");
var parsebytes = new byte[attribute.ReservedLength];
Array.Copy(bytes, (int)numBytes, parsebytes, 0, attribute.ReservedLength);
numBytes += attribute.ReservedLengthInBytes;
value = attribute.Type switch
{
S7StringType.S7String => S7String.FromByteArray(parsebytes),
S7StringType.S7WString => S7WString.FromByteArray(parsebytes),
_ => throw new ArgumentException("Please use a valid string type for the S7StringAttribute")
};

[Jason-Jelks]

Thanks for the heads up, I will check it.
Which framework are you using .Net Framework, .Net Standard or .NET5?
What model of PLC are you connecting too?

[Jason-Jelks]

@dhullett08 - It appears yesterday's commit had some merge issues, which I don't have time to look into at this moment. feel free to pull from my tree: jjelks for the latest update, which is working for me on the S7-1200 & S7-1500.

[dhullett08]

@Jason-Jelks I am using S71500S software PLC on a Siemens Microbox PC and .NET 5.0. I tried full framework as well and I couldn't get classes to work? Thats when I went and started digging on MSDN and noticed that it states to GetCustomAttributes of a property it has to be a PropertyInfo object and the method needs called on the instance, not the underlying type (System.String). For the Struct using FieldInfo works because it is for that instance of a Field. I'm not sure what the disconnect is if it works for you.