# Value Converters

> Use MeasureConverter, ColorConverter, BooleanConverter and LogarithmicConverter to show twips in points, text colors, list formats and a zoom slider in WPF.

- **Product:** TX Text Control .NET for WPF
- **Section:** Documentation
- **Kind:** Topic
- **Path:** TX Text Control .NET for WPF > Integration Guide > Data Binding > Value Converters
- **3247 words**
- **Web URL:** https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/value-converters/
- **LLMs URL:** https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/value-converters/llms.txt
- **LLMs-Full URL:** https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/value-converters/llms-full.txt

---

TX Text Control measures distances in twips, a twentieth of a point, and its `InputFormat` reports colors as `System.Drawing.Color` and list formats as enumeration values. WPF controls expect other types: text, `double` values in device-independent units, `System.Windows.Media.Color`, `bool`. Four value converters of the namespace `TXTextControl.WPF` translate between the two in a binding, so that a text box, a color swatch, a radio button or a slider can show and change the editor's values without code-behind.

| Converter | From the editor | To the WPF control | Typical use |
|---|---|---|---|
| [MeasureConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/measureconverter/llms-full.txt) | `int` in twips | `string` or `double` in another unit | Font sizes, indents, paragraph distances |
| [ColorConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/colorconverter/llms-full.txt) | `System.Drawing.Color` | `System.Windows.Media.Color` | Text and background colors |
| [BooleanConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/booleanconverter/llms-full.txt) | An enumeration value, `int`, `char` or `bool?` | `bool` | Radio buttons, check marks in menus, toggle buttons |
| [LogarithmicConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/llms-full.txt) | A number on a linear scale | A number on a logarithmic scale | A zoom slider |

Each of them implements `IValueConverter`, and each converts in both directions: `Convert` for values from the editor, `ConvertBack` for values the user enters. When a value can't be converted, both return `DependencyProperty.UnsetValue`.

### Declare a Converter

A converter is an object in the resources, created once and used by any number of bindings through its key. The window declares the prefix of TX Text Control and the converters in its resources:

```xml
<Window x:Class="MyWPFApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:WPF="clr-namespace:TXTextControl.WPF;assembly=TXTextControl.WPF"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <WPF:MeasureConverter x:Key="pointConv" Unit="Point" Decimals="1" />
        <WPF:MeasureConverter x:Key="cmConv" Unit="Centimeter" Decimals="2" ShowAllDecimals="True" />
        <WPF:ColorConverter x:Key="colorConv" />
        <WPF:BooleanConverter x:Key="boolConv" />
        <WPF:LogarithmicConverter x:Key="logConv"
                                  InputMinimum="10" InputCenter="100" InputMaximum="400"
                                  OutputMinimum="0" OutputMaximum="100" />
    </Window.Resources>
    <DockPanel>
        <!-- The controls of the following sections go here -->
        <WPF:TextControl x:Name="textControl1" />
    </DockPanel>
</Window>
```

A binding names the converter with `Converter={StaticResource key}`. To use the same converters in every window, declare them once in *App.xaml* or a resource dictionary, as [Resource Dictionaries and Styling](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/styling/llms-full.txt) shows.

### Show Measures in Points or Centimeters

[MeasureConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/measureconverter/llms-full.txt) converts a value in twips into the unit that its [Unit](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/measureconverter/unit-property/llms-full.txt) property names, and back:

| `Unit` | The converted value is in |
|---|---|
| `Point` | Points, 1/72 inch |
| `Centimeter` | Centimeters |
| `Millimeter` | Millimeters |
| `CentiInch` | 1/100 inch |
| `StandardWPF` | 1/96 inch, the device-independent units of WPF |
| `Twips` | Twips, 1/1440 inch |

The type of the target decides whether the result is a `string` or a `double`. [Decimals](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/measureconverter/decimals-property/llms-full.txt) sets the number of decimals, and [ShowAllDecimals](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/measureconverter/showalldecimals-property/llms-full.txt) whether a string shows all of them: with three decimals, 15.5 becomes `15.500` when it is `true` and `15.5` when it is `false`.

The following text boxes show the font size at the input position in points and the space above the paragraph in centimeters. Typing a new value changes the selected text:

```xml
<ToolBar DockPanel.Dock="Top">
    <TextBox x:Name="fontSizeTextBox" Width="50"
             Text="{Binding ElementName=textControl1, Path=InputFormat.FontSize,
                            Converter={StaticResource pointConv}, Mode=TwoWay}" />
    <TextBox x:Name="topDistanceTextBox" Width="60"
             Text="{Binding ElementName=textControl1, Path=InputFormat.TopDistance,
                            Converter={StaticResource cmConv}, Mode=TwoWay}" />
</ToolBar>
```

[InputFormat.FontSize](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/fontsize-property/llms-full.txt) and [InputFormat.TopDistance](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/topdistance-property/llms-full.txt) are both in twips. A `TextBox` updates its source when it loses the focus, so the new size applies when the user leaves the box.

### Show the Text Color

[ColorConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/colorconverter/llms-full.txt) converts a `System.Drawing.Color` into a `System.Windows.Media.Color`, the type of the `Color` property of a WPF brush. The following swatch shows the color of the text at the input position:

```xml
<Rectangle Width="16" Height="16" Margin="4,0">
    <Rectangle.Fill>
        <SolidColorBrush Color="{Binding ElementName=textControl1, Path=InputFormat.TextColor,
                                         Converter={StaticResource colorConv}}" />
    </Rectangle.Fill>
</Rectangle>
```

[InputFormat.TextColor](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/textcolor-property/llms-full.txt) and [TextBackColor](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/textbackcolor-property/llms-full.txt) have the type `System.Drawing.Color?`. `ConvertBack` works as well, so a color picker whose selected color is a `System.Windows.Media.Color` can set the text color through a two-way binding.

### Check a Radio Button for a List Format

[BooleanConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/booleanconverter/llms-full.txt) returns `true` when the converter parameter is the string representation of the value. With an enumeration property such as [InputFormat.NumberedListFormat](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/numberedlistformat-property/llms-full.txt), each radio button names the value it stands for:

```xml
<RadioButton Content="1, 2, 3" GroupName="numberFormat" Focusable="False"
             IsChecked="{Binding ElementName=textControl1, Path=InputFormat.NumberedListFormat,
                                 Converter={StaticResource boolConv}, ConverterParameter=ArabicNumbers}" />
<RadioButton Content="a, b, c" GroupName="numberFormat" Focusable="False"
             IsChecked="{Binding ElementName=textControl1, Path=InputFormat.NumberedListFormat,
                                 Converter={StaticResource boolConv}, ConverterParameter=Letters}" />
```

The values are those of the [NumberFormat](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/numberformat/enumeration/llms-full.txt) enumeration, such as `ArabicNumbers`, `Letters`, `CapitalLetters`, `RomanNumbers` and `SmallRomanNumbers`. When a radio button is checked, `ConvertBack` returns its parameter, and the list format of the selected paragraphs changes. When it is unchecked, `ConvertBack` returns `DependencyProperty.UnsetValue`, so that only the checked button of the group sets a value.

The converter supports `System.Enum`, `int`, `int?`, `bool?`, `char` and `char?`. For a `bool?` source, such as [InputFormat.Bold](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol/inputformat/bold-property/llms-full.txt), it converts to `bool` without a parameter, which suits a `MenuItem` with `IsCheckable="True"`.

### Zoom With a Slider

A zoom slider that runs from 10 to 400 percent in a straight line leaves little room for the values around 100 percent that users choose most. [LogarithmicConverter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/llms-full.txt) maps the linear range of the slider to a logarithmic one:

```xml
<Slider x:Name="zoomSlider" DockPanel.Dock="Bottom" Minimum="0" Maximum="100"
        Value="{Binding ElementName=textControl1, Path=ZoomFactor,
                        Converter={StaticResource logConv}}" />
```

The resource defines the ranges:

- [InputMinimum](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/inputminimum-property/llms-full.txt) and [InputMaximum](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/inputmaximum-property/llms-full.txt), 10 and 400, are the range of the source, here [ZoomFactor](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/textcontrol/zoomfactor-property/llms-full.txt) in percent. Smaller or larger values are treated as the bounds.
- [InputCenter](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/inputcenter-property/llms-full.txt), 100, is the source value that lands in the middle of the slider.
- [OutputMinimum](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/outputminimum-property/llms-full.txt) and [OutputMaximum](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/reference/txtextcontrol-wpf/logarithmicconverter/outputmaximum-property/llms-full.txt), 0 and 100, match the `Minimum` and `Maximum` of the slider.

`ZoomFactor` is a dependency property, and the `Value` of a slider binds in both directions by default, so moving the slider zooms the document without a handler.

### When No Converter Fits

For other conversions, write a class that implements `System.Windows.Data.IValueConverter`, declare it in the resources in the same way and name it in the binding. The converters of TX Text Control show the pattern to follow: return `DependencyProperty.UnsetValue` for a value that can't be converted, and handle `null`, which `InputFormat` returns when the selected text has no common value.

### Next Steps

- [Binding Document Content](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/document-content/llms-full.txt): the bindings to `InputFormat` and to the whole document.
- [Resource Dictionaries and Styling](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/styling/llms-full.txt): converters and styles for the whole application.
- [Data Binding](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/llms-full.txt): how bindings to the `TextControl` work.

---

## Nearby

- **Previous:** [Binding Document Content](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/data-binding/document-content/llms-full.txt)
- **Next:** [MVVM Integration Patterns](https://docs.textcontrol.com/tx-text-control-dotnet-wpf/integration/mvvm/llms-full.txt)