function GetComponent(i: Integer): TNetComponent;
function GetProperty(i: Integer): TNetProperty;
function GetProperty(i: Integer): TNetProperty;
property Components[i: Integer]: TNetComponent read GetComponent;
property Properties[i: Integer]: TNetProperty read GetProperty;
property Properties[i: Integer]: TNetProperty read GetProperty;
Later will flag an error in FI. It seems that you accept a simple +s plural but not ies plural.