Hello Nebojsa,

You can change the color of the whole number in the textbox area of the RadCalculatorPicker control via its Foreground property. You can change the property based on the Value of the control. One way to do this is to implement an IValueConverter. For example:

public class NumberToBrushConverter : IValueConverter
{
	public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
	{
		double number = System.Convert.ToDouble(value);
		return number >= 0d && number <= 5000d ? Brushes.Green : Brushes.Red;
	}

	public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
	{
		throw new NotImplementedException();
	}
}

<telerik:RadCalculatorPicker x:Name="calculatorPicker"
							 Foreground="{Binding ElementName=calculatorPicker, Path=Value, Converter={StaticResource NumberToBrushConverter}}"/>

To change the sign of the value using the N key, you can subscribe to the KeyDown event of the picker and update the Value property accordingly.  I also logged a couple of feature requests for this and for the numeric operator visibility requirement.

• Add keyboard support for changing the sign of the value
• Add new visualization mode for the text input of RadCalculatorPicker

I am closing this feature because it contains multiple feature requests. Please follow the items linked in the list above.

Regards,
Martin Ivanov
Progress Telerik

Hello Nebojsa,

Thank you for the additional feedback.

Regards,
Martin Ivanov
Progress Telerik

Hello Nebojsa,

Thank you for the additional information. Let's see if I understand this correctly with the following summary. You need for the TextBox part of the control to:

• be able to set the floating number format of the entered number. As in your example, where you want to see two trailing zeroes after the decimal point. This should be doable by setting a string format like "{0:F2}" if such API existed.
• be able to add thousands separator, so instead of showing (for example) 10000, to show 10,000.
• be able to type decimal numbers.
• display the whole expression instead of showing only the result. Note that the idea of the TextBox is mostly to show the result in a simple manner, so showing the full expression will require replacement of the visual element showing the input and also the logic behind it. However, here you can consider an approach with an additional UI element placed near the RadCalculatorPicker which is bound to the History property of the picker. 
• be able to set color for each separate digit in the TextBox. Here I will need some more context. Do you need to color each digit the text in the TextBox or the color of numbers shown in the History?
• be able to set maximum number of decimal places for the entered number.

Please correct me if I am wrong.

I wanted to summarize this in order to have it in one place and then to log few separate feature requests where meaningful.

Regards,
Martin Ivanov
Progress Telerik

Hello Nebojsa,

Can you tell me what other options exactly do you need? Do you mean that you want to be able to provide a NumberFormatInfo that allows different kinds of options?

Regards,
Martin Ivanov
Progress Telerik