title | author | description | ms.date |
---|---|---|---|
TextValidationBehavior - .NET MAUI Community Toolkit |
bijington |
The TextValidationBehavior is a Behavior that allows the user to validate a given text depending on specified parameters. |
04/20/2022 |
The TextValidationBehavior
is a Behavior
that allows the user to validate a given text depending on specified parameters. By adding this behavior to any InputView
control it can be styled differently depending on whether a valid or an invalid text value is provided. It offers various built-in checks such as checking for a certain length or whether or not the input value matches a specific regular expression.
[!INCLUDE important note on bindings within behaviors]
The following examples show how to add the TextValidationBehavior
to an Entry
and change the TextColor
based on whether the entered text is between 1 and 10 characters long.
[!INCLUDE XAML usage guidance]
The TextValidationBehavior
can be used as follows in XAML:
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
x:Class="CommunityToolkit.Maui.Sample.Pages.Behaviors.TextValidationBehaviorPage">
<ContentPage.Resources>
<Style x:Key="InvalidEntryStyle" TargetType="Entry">
<Setter Property="TextColor" Value="Red" />
</Style>
<Style x:Key="ValidEntryStyle" TargetType="Entry">
<Setter Property="TextColor" Value="Green" />
</Style>
</ContentPage.Resources>
<Entry>
<Entry.Behaviors>
<toolkit:TextValidationBehavior
InvalidStyle="{StaticResource InvalidEntryStyle}"
ValidStyle="{StaticResource ValidEntryStyle}"
Flags="ValidateOnValueChanged"
MinimumLength="1"
MaximumLength="10" />
</Entry.Behaviors>
</Entry>
</ContentPage>
The TextValidationBehavior
can be used as follows in C#:
class TextValidationBehaviorPage : ContentPage
{
public TextValidationBehaviorPage()
{
var entry = new Entry();
var validStyle = new Style(typeof(Entry));
validStyle.Setters.Add(new Setter
{
Property = Entry.TextColorProperty,
Value = Colors.Green
});
var invalidStyle = new Style(typeof(Entry));
invalidStyle.Setters.Add(new Setter
{
Property = Entry.TextColorProperty,
Value = Colors.Red
});
var textValidationBehavior = new TextValidationBehavior
{
InvalidStyle = invalidStyle,
ValidStyle = validStyle,
Flags = ValidationFlags.ValidateOnValueChanged,
MinimumLength = 1,
MaximumLength = 10
};
entry.Behaviors.Add(textValidationBehavior);
Content = entry;
}
}
Our CommunityToolkit.Maui.Markup
package provides a much more concise way to use this Behavior
in C#.
using CommunityToolkit.Maui.Markup;
class TextValidationBehaviorPage : ContentPage
{
public TextValidationBehaviorPage()
{
Content = new Entry()
.Behaviors(new TextValidationBehavior
{
InvalidStyle = new Style<Entry>(Entry.TextColorProperty, Colors.Red),
ValidStyle = new Style<Entry>(Entry.TextColorProperty, Colors.Green),
Flags = ValidationFlags.ValidateOnValueChanged,
MinimumLength = 1,
MaximumLength = 10
});
}
}
The following screenshot shows the resulting TextValidationBehavior on Android:
Property | Type | Description |
---|---|---|
DecorationFlags |
TextDecorationFlags |
Provides enumerated value to use to set how to handle white spaces. |
MaximumLength |
int |
The maximum length of the value that will be allowed. |
MinimumLength |
int |
The minimum length of the value that will be allowed. |
RegexOptions |
RegexOptions |
Provides enumerated values to use to set regular expression options. |
RegexPattern |
string |
The regular expression pattern which the value will have to match before it will be allowed. |
[!INCLUDE common validation properties]
You can find an example of this behavior in action in the .NET MAUI Community Toolkit Sample Application.
You can find the source code for TextValidationBehavior
over on the .NET MAUI Community Toolkit GitHub repository.