Restriction or Validation in WPF Double TextBox

6 Jul 20216 minutes to read

This section explains how to validate or restrict the DoubleTextBox control value.

Restrict the value within minimum and maximum value

The Value of the DoubleTextBox can be restricted within the maximum and minimum limits. Once the value has reached the maximum or minimum value , the value does not exceed the limit. We can change the maximum and minimum limits by using the MinValue property and MaxValue property.

You can choose when to validate the maximum and minimum limits while changing the values by using the MinValidation and MaxValidation properties.

• OnKeyPress — When setting the MaxValidation or MinValidation to OnKeyPress, the value in the DoubleTextBox will be validated shortly after pressing a key. So, it is not possible to provide any invalid input at all and the value does not exceed the maximum and minimum limits.

• OnLostFocus - When setting MaxValidation or MinValidation to OnLostFocus, the value in the DoubleTextBox is validated, when the DoubleTextBox loses the focus. That is, the DoubleTextBox will accept any value, validation will only take place after the DoubleTextBox has lost its keyboard focus. After validation, when the value of the DoubleTextBox is greater than the MaxValue or less than the MinValue, the value will be automatically set to MaxValue or MinValue.

• MaxValueOnExceedMaxDigit - When you give input greater than specified maximum limit, MaxValueOnExceedMaxDigit property will decide either it should retain the old value or reset to maximum limit that is specified. For example, if MaxValue is set to 100 and you are trying to input 200. Value will changed to 100 when MaxValueOnExceedMaxDigit is true. When MaxValueOnExceedMaxDigit is false, 20 will be retained and last entered 0 will be ignored.

  NOTE

  MaxValueOnExceedMinDigit property will be enabled only when the MaxValidation is set to OnKeyPress.

• MinValueOnExceedMinDigit - When you give input less than specified minimum limit, MinValueOnExceedMinDigit property will decide either it should retain the old value or reset to minimum limit that is specified. For example, if MinValue is set to 200 and the Value is 205 and you are trying change the value to 20. Value will changed to 200 when MinValueOnExceedMinDigit is true. When MinValueOnExceedMinDigit is false, Old value 205 will be retained.

  NOTE

  MinValueOnExceedMinDigit will be enabled only when the MinValidation is set to OnKeyPress.

XAML

<syncfusion:DoubleTextBox x:Name="doubleTextBox" Width="150" MaxValue="100" MinValue="10"
                          MinValueOnExceedMinDigit="True" MaxValueOnExceedMaxDigit="True"
                          MinValidation="OnKeyPress" MaxValidation="OnLostFocus"/>

C#

DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Width = 150;
doubleTextBox.Height = 25;
doubleTextBox.MinValue = 10;
doubleTextBox.MaxValue =100;
doubleTextBox.MinValidation = MinValidation.OnKeyPress;
doubleTextBox.MaxValidation = MaxValidation.OnLostFocus;
doubleTextBox.MinValueOnExceedMinDigit = true;
doubleTextBox.MaxValueOnExceedMaxDigit = true;

MinValidation is set to OnKeyPress, it cannot let to enter a value less than the MinValue. If try to enter a value less than the MinValue, then the MinValue will set to the Value property because MinValueOnExceedMinDigit is set to true.

MaxValidation is set to OnLostFocus, so the MaxValidation will be performed only in the lost focus.

Restrict number of decimal digit

You can format the decimal digits in the DoubleTextBox control using NumberDecimalDigits property. You can restrict the decimal digits of the text within maximum and minimum limits in DoubleTextBox control using MinimumNumberDecimalDigits and MaximumNumberDecimalDigits properties. The default value of MinimumNumberDecimalDigits,MaximumNumberDecimalDigits and DoubleDecimalDigits properties is -1.

NOTE

If the value of MinimumNumberDecimalDigits property is greater than the value of MaximumNumberDecimalDigits property, the text of DoubleTextBox will be updated based on the value of MinimumNumberDecimalDigits property.

XAML

<syncfusion:DoubleTextBox Value="125.32545" HorizontalAlignment="Center" VerticalAlignment="Center"
                            MaximumNumberDecimalDigits="4"
                            MinimumNumberDecimalDigits="1" />

C#

DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Value = 125.32545;
doubleTextBox.MaximumNumberDecimalDigits = 4;
doubleTextBox.MinimumNumberDecimalDigits = 1;

When value of MinimumNumberDecimalDigits, MaximumNumberDecimalDigits and NumberDecimalDigits properties are specified, NumberDecimalDigits property takes high precedence and updates the text of DoubleTextBox property.

XAML

<syncfusion:DoubleTextBox Value="125.32545" HorizontalAlignment="Center" VerticalAlignment="Center"
                            MaximumNumberDecimalDigits="4"
                            MinimumNumberDecimalDigits="1" 
                            NumberDecimalDigits="3"
                            />

C#

DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Value = 125.32545;
doubleTextBox.MaximumNumberDecimalDigits = 4;
doubleTextBox.MinimumNumberDecimalDigits = 1;
doubleTextBox.NumberDecimalDigits = 3;

Read only mode

The DoubleTextBox cannot allow the user input, edits when IsReadOnly property is sets to true. The user can still select text and display the cursor on the DoubleTextBox by setting the IsReadOnlyCaretVisible property to true. However, value can be changed programmatically in readonly mode.

XAML

<syncfusion:DoubleTextBox x:Name="doubleTextBox" IsReadOnly="True" Value="10" IsReadOnlyCaretVisible="True"/>

C#

DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Value = 10;
doubleTextBox.IsReadOnly = true;
doubleTextBox.IsReadOnlyCaretVisible = true;