Nullability of reference types in type of parameter 'parameter' of 'bool CommandHelper.CanExecute(object parameter)' doesn't match implicitly implemented member 'bool ICommand.CanExecute(object? parameter)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'parameter' of 'void CommandHelper.Execute(object parameter)' doesn't match implicitly implemented member 'void ICommand.Execute(object? parameter)' (possibly because of nullability attributes).

Nullability of reference types in type of 'event EventHandler CommandHelper.CanExecuteChanged' doesn't match implicitly implemented member 'event EventHandler? ICommand.CanExecuteChanged'.

Nullability of reference types in type of 'event PropertyChangedEventHandler ViewModelBase.PropertyChanged' doesn't match implicitly implemented member 'event PropertyChangedEventHandler? INotifyPropertyChanged.PropertyChanged'.

Dereference of a possibly null reference.

Possible null reference argument for parameter 's' in 'double double.Parse(string s)'.

The variable 'ex' is declared but never used

Possible null reference return.

Possible null reference argument for parameter 'value' in 'object Enum.Parse(Type enumType, string value)'.