WPF problem with using decimal points with ValidationRule and Lost Focus

I create an int ValidationRule demo due to having no relevant information about decimal points with ValidationRule, below is my sample code:
Xaml code:

 <Window.DataContext>  
        <local:ViewModel></local:ViewModel>  
    </Window.DataContext>  
<Window.Resources>  
    <local:MyConverter x:Key="MyConver"></local:MyConverter>  
</Window.Resources>  
    <Grid>  
        <TextBox  Name="TextBox1"  Width="50"   Margin="0,0,10,0" Height="21"  FontSize="12" ToolTip="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}" >  
            <TextBox.Text>  
                <Binding Path="SetTemperature" UpdateSourceTrigger="PropertyChanged" >  
                    <Binding.ValidationRules>  
                        <local:AgeRangeRule Min="21" Max="130"/>  
                    </Binding.ValidationRules>  
                </Binding>  
            </TextBox.Text>  
        </TextBox>  
        <Button Content="Button" Width="120" Height="50" VerticalAlignment="Top" IsEnabled="{Binding ElementName=TextBox1,Path=(Validation.HasError),Converter={StaticResource MyConver}}"></Button>  
    </Grid>  

C# code:

 public class AgeRangeRule : ValidationRule  
    {  
        public int Min { get; set; }  
        public int Max { get; set; }  
  
        public AgeRangeRule()  
        {  
        }  
  
        public override ValidationResult Validate(object value, CultureInfo cultureInfo)  
        {  
            int age = 0;  
  
            try  
            {  
                if (((string)value).Length > 0)  
                    age = Int32.Parse((String)value);  
            }  
            catch (Exception e)  
            {  
                return new ValidationResult(false, $"Illegal characters or {e.Message}");  
            }  
  
            if ((age < Min) || (age > Max))  
            {  
                return new ValidationResult(false,  
                  $"Please enter an age in the range: {Min}-{Max}.");  
            }  
            return ValidationResult.ValidResult;  
        }  
    }  
public class ViewModel  
    {  
        public int SetTemperature { get; set; }  
        public ViewModel()  
        {  
            SetTemperature = 50;  
        }  
    }  
  
    public class MyConverter : IValueConverter  
    {  
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)  
        {  
            bool flag = (bool)value;  
            flag = !flag;  
            return flag;  
        }  
  
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)  
        {  
            throw new NotImplementedException();  
        }  
    }  

The result picture is:

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