Changing Double Value in WPF Double TextBox

The DoubleTextBox allows the user to change the value using the Value property.

<syncfusion:DoubleTextBox x:Name="doubleTextBox" Height="25"
                          Width="150" Value="10"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Width = 150;
doubleTextBox.Height = 25;
doubleTextBox.Value = 10;

DoubleTextBox displaying a value

Data binding is the process of establishing a connection between the application UI and business logic. Data binding can be unidirectional (source -> target or target <- source) or bidirectional (source <-> target). By assigning a value to the Value property by binding, you can change the DoubleTextBox value.

The following code snippets illustrate the value binding from one DoubleTextBox to another.

<syncfusion:DoubleTextBox x:Name="doubleTextBox1" Value="{Binding MyValue,UpdateSourceTrigger=PropertyChanged}" Height="25" Width="100"/>
<syncfusion:DoubleTextBox x:Name="doubleTextBox2" Value="{Binding MyValue,UpdateSourceTrigger=PropertyChanged}" Width="100" Height="25"  />

ViewModel.cs

class ViewModel : NotificationObject
{
    private double myValue;
    public double MyValue
    {
        get
        {
            return myValue;
        }
        set
        {
            myValue = value;
            RaisePropertyChanged("MyValue");
        }
    }
}

Binding a value to DoubleTextBox

Change double value by pasting the clipboard’s text

By default, DoubleTextBox simply replaces the whole value by copied value with the current number format. If you want to replace or insert the copied value on specific place, use the PasteMode property value as Advanced. The default value of PasteMode property is Default.

The following table explains the pasting behaviour in Advanced paste mode,

S.No Action Pasting behaviour in Advanced paste mode
1 When the whole value is selected It simply replaces the whole value by copied value with the current number format.
2 When the cursor is at some position and the copied value does not contain a number decimal separator It inserts the copied value into the current cursor position.
3 When the cursor is at some position and the copied value contains a number decimal separator It won’t perform pasting operation.
4 When the cursor is at some position and the control value is 0 or null It simply replaces the whole value by copied value with the current number format.
5 When a part of the number is selected If the selected value contains a number decimal separator, then copied value must contain number decimal separator. Otherwise, it won’t perform pasting operation. If the selected text does not contain a number decimal separator, then copied value must not contain number decimal separator. Otherwise, it won’t perform pasting operation.
<syncfusion:DoubleTextBox PasteMode="Advanced" 
                           Value="12345.67"
                           Name="doubleTextBox"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.PasteMode = PasteMode.Advanced;
doubleTextBox.Value = 12345.67;

DoubleTextBox pasting the copied value in specific place

Value Changed Event

The DoubleTextbox control can notify changes in value through the ValueChanged event. In ValueChanged event, you can get old value and new value from the OldValue and NewValue properties.

<syncfusion:DoubleTextBox ValueChanged="DoubleTextBox_ValueChanged"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.ValueChanged += new PropertyChangedCallback(DoubleTextBox_ValueChanged);

You can handle the event as follows:

private void DoubleTextBox_ValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    // Get old and new value
    var newValue = e.NewValue;
    var oldValue = e.OldValue;
}

Setting the Null value

By default, the DoubleTextBox control will display zero value when the Value is set to null. You can use the NullValue and UseNullOption properties to show the null or any other value instead of zero.

The default value of the NullValue property is null, you can reset this to any other double value. It will display only on setting the UseNullOption property is set to true.

NullValue = Null

<syncfusion:DoubleTextBox x:Name="doubleTextBox" Height="25"
                          Width="100" UseNullOption="True"  NullValue="{x:Null}"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Width = 100;
doubleTextBox.Height = 25;
doubleTextBox.NullValue = null;
doubleTextBox.UseNullOption = true;

Setting null as NullValue in DoubleTextBox

NullValue = 10

<syncfusion:DoubleTextBox x:Name="doubleTextBox" Height="25"
                          Width="100" UseNullOption="True" NullValue="10"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Width = 100;
doubleTextBox.Height = 25;
doubleTextBox.NullValue = 10;
doubleTextBox.UseNullOption = true;

Setting Null value in DoubleTextBox

Setting Watermark Text

We can display certain information within the control by using the WaterMarkText property. WaterMarkText is shown when the WatermarkTextIsVisible property is true and the value is null or empty, the control is not in focus and the UseNullOption property is true.

Setting the WatermarkText Foreground

The DoubleTextBox allows you to set the desired brush as a foreground for WaterMarkText using WaterMarkTextForeground property. The default color of WaterMarkTextForeground is Black.

<syncfusion:DoubleTextBox x:Name="doubleTextBox" Width="100"
                          Height="25" UseNullOption="True" WatermarkText="Type here"
                          WatermarkTextIsVisible="True" WatermarkTextForeground="Red"/>
DoubleTextBox doubleTextBox = new DoubleTextBox();
doubleTextBox.Width = 100;
doubleTextBox.Height = 25;
doubleTextBox.UseNullOption = true;
doubleTextBox.WatermarkText = "Type Here";
doubleTextBox.WatermarkTextIsVisible = true;
doubleTextBox.WatermarkTextForeground = Brushes.Red;

DoubleTextBox displaying a watermark text in red color

Setting Watermark Template

You can customize the Visual appearance of the WatermarkText by using the WatermarkTemplate property.

  • xaml
  • <syncfusion:DoubleTextBox x:Name="doubleTextBox" Width="100" Height="25"
                              WatermarkText="Type Here" CornerRadius="3" 
                              WatermarkTextIsVisible="True" WatermarkOpacity="0.5" 
                              UseNullOption="True">
        <syncfusion:DoubleTextBox.WatermarkTemplate >
            <DataTemplate>
                <Border Background="Red">
                    <TextBlock Text="{Binding}" VerticalAlignment="Center" Margin="5,0,0,0"/>
                </Border>
            </DataTemplate>
        </syncfusion:DoubleTextBox.WatermarkTemplate>
    </syncfusion:DoubleTextBox>

    DoubleTextBox displaying watermark text using a data-template

    NOTE

    The UseNullOption property must be enabled if you want to see NullValue or WaterMarkText in DoubleTextBox control.

    NOTE

    If both NullValue and WaterMarkText are specified, you will only see NullValue but not WaterMarkText.