Using method from another class in Xamarin - xaml

Question

I am using Xamarin Cross Platform and Windows 10.
Trying to add behavior on entry. Had class Behaviors:
using System;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms;
namespace CoTraveller
{
public class Behaviors
{
public class NumericValidationBehavior : Behavior<Entry>
{
protected override void OnAttachedTo(Entry entry)
{
entry.TextChanged += OnEntryTextChanged;
base.OnAttachedTo(entry);
}
protected override void OnDetachingFrom(Entry entry)
{
entry.TextChanged -= OnEntryTextChanged;
base.OnDetachingFrom(entry);
}
public void OnEntryTextChanged(object sender, TextChangedEventArgs args)
{
double result;
bool isValid = double.TryParse(args.NewTextValue, out result);
((Entry)sender).TextColor = isValid ? Color.Default : Color.Red;
}
}
}
}
Xaml page where I want to use this class method:
<?xml version="1.0" encoding="utf-8" ?> <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:CoTraveller"
x:Class="CoTraveller.RegistrationPage">
<ContentPage.Content>
<ScrollView>
<StackLayout VerticalOptions="CenterAndExpand" Padding="5">
<StackLayout Orientation="Horizontal">
<Entry x:Name="name_entry" Placeholder="First Name">
<Entry.Behaviors>
<local:NumericValidationBehavior />
</Entry.Behaviors>
</Entry>
<Entry x:Name="surname_entry" Placeholder="Surname"></Entry>
</StackLayout>
<Entry Placeholder="Login"></Entry>
<StackLayout Orientation="Horizontal">
<Entry x:Name="pass_entry" Placeholder="Password" IsPassword="True"></Entry>
<Entry x:Name="pass_confirm_entry" Placeholder="Confirm Password" IsPassword="True"></Entry>
</StackLayout>
<StackLayout Orientation="Horizontal">
<Label Text="Save Password"></Label>
<Switch IsToggled="False"></Switch>
</StackLayout>
<Label Text="Date Of Birth"></Label>
<DatePicker x:Name="birthday_dp"></DatePicker>
<Picker x:Name="sex_p" HorizontalOptions="FillAndExpand" Title="Click and select gender">
<Picker.Items>
<x:String>Male</x:String>
<x:String>Female</x:String>
</Picker.Items>
</Picker>
<Entry Placeholder="Email (optional)"></Entry>
<Entry Placeholder="Phone number (optional)"></Entry>
<Picker x:Name="type_entry" HorizontalOptions="FillAndExpand" Title="Click and select user type">
<Picker.Items>
<x:String>Driver</x:String>
<x:String>Pedestrian</x:String>
</Picker.Items>
</Picker>
<Button Text="Sign Up" Clicked="SignUpBtn"></Button>
<Label x:Name="sign_in_lbl" Text="Already have account? Sign In" TextColor="Blue"></Label>
</StackLayout>
</ScrollView>
</ContentPage.Content> </ContentPage>
Both are in the same namespace and CoTraveller is the name of my project.
I had errors like:
Severity Code Description Project File Line Suppression State
Error Position 12:30. Type local:NumericValidationBehavior not found in xmlns clr-namespace:CoTraveller CoTraveller D:\CoTraveller\CoTraveller\CoTraveller\RegistrationPage.xaml 12
Severity Code Description Project File Line Suppression State
Error XLS0414 The type 'local:NumericValidationBehavior' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built. CoTraveller RegistrationPage.xaml 12
What is the reason? I declared namespace in XAML file, but smth is wrong...

Answer 1

The namespace declaration xmlns:local="clr-namespace:CoTraveller" is correct, but because the behavior is a nested type, you need to qualify the name with the outer type where you use it. Use <local:Behaviors.NumericValidationBehavior />.