C#•3y ago

WPF Validation

Hi, I'm struggling with the validation part of my project. I've created this Viewmodel to experiment the validation.
But now i do not understand how can i make a dialog to get back individually radius or roll position using the validation from this viewmodel.
Here is my DialogView which is openned when i double click on the textbox which display radius or rollposition:

public class SymmetricRollViewModel : ViewModelModelBase<SymmetricRoll, SymmetricRollViewModel>, INotifyDataErrorInfo
    {
        public string Error
        {
            get { return string.Empty; }
        }
        public Dictionary<string, string> ErrorCollection { get; private set; } = new Dictionary<string, string>();
        public string this[string columnName]
        {
            get
            {
                string result = string.Empty;

                switch(columnName)
                {
                    case "RollPosition":
                        if(string.IsNullOrWhiteSpace(RollPosition))
                            result = "RollPosition cannot be empty";
                        if(double.TryParse(RollPosition, out double value))
                            if(value > 10)
                                result = $"value false {value}";
                        break;
                }

                if(ErrorCollection.ContainsKey(columnName))
                    ErrorCollection[columnName] = result;
                else if(result != null)
                    ErrorCollection.Add(columnName, result);

                OnPropertyChanged(nameof(ErrorCollection));
                return result;
            }
        }
        public event EventHandler<DataErrorsChangedEventArgs>? ErrorsChanged;
        public bool HasErrors
        {
            get { return false; }
        }

        private double _rollPosition;
        public double RollPosition
        {
            get => _rollPosition;
            set
            {
                _rollPosition = value;
                OnPropertyChanged();
            }
        }

        private double _radius;
        public double Radius
        {
            get { return _radius; }
            set
            {
                _radius = value;
                OnPropertyChanged();
            }
        }

        public long WidthId => _symmetricRoll.WidthId;
    }

public class SymmetricRollViewModel : ViewModelModelBase<SymmetricRoll, SymmetricRollViewModel>, INotifyDataErrorInfo
    {
        public string Error
        {
            get { return string.Empty; }
        }
        public Dictionary<string, string> ErrorCollection { get; private set; } = new Dictionary<string, string>();
        public string this[string columnName]
        {
            get
            {
                string result = string.Empty;

                switch(columnName)
                {
                    case "RollPosition":
                        if(string.IsNullOrWhiteSpace(RollPosition))
                            result = "RollPosition cannot be empty";
                        if(double.TryParse(RollPosition, out double value))
                            if(value > 10)
                                result = $"value false {value}";
                        break;
                }

                if(ErrorCollection.ContainsKey(columnName))
                    ErrorCollection[columnName] = result;
                else if(result != null)
                    ErrorCollection.Add(columnName, result);

                OnPropertyChanged(nameof(ErrorCollection));
                return result;
            }
        }
        public event EventHandler<DataErrorsChangedEventArgs>? ErrorsChanged;
        public bool HasErrors
        {
            get { return false; }
        }

        private double _rollPosition;
        public double RollPosition
        {
            get => _rollPosition;
            set
            {
                _rollPosition = value;
                OnPropertyChanged();
            }
        }

        private double _radius;
        public double Radius
        {
            get { return _radius; }
            set
            {
                _radius = value;
                OnPropertyChanged();
            }
        }

        public long WidthId => _symmetricRoll.WidthId;
    }