You can bind the ViewModel command to external ItemTemplate of Xamarin.Forms SfListView by using RelativeBinding in command binding.
XAML: ListView definition
<syncfusion:SfListView x:Name="listView"
ItemSpacing="1"
ItemsSource="{Binding contactsinfo}">
<syncfusion:SfListView.ItemTemplate >
<DataTemplate>
<local:TemplateViewCell/>
</DataTemplate>
</syncfusion:SfListView.ItemTemplate>
</syncfusion:SfListView>
XAML: ViewCell definition
Binding the ViewModel command for button in ViewCell using AncestorType in RelativeBinding.
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ListViewXamarin.TemplateViewCell">
<ViewCell.View>
<Grid x:Name="grid" RowSpacing="0">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="1" />
</Grid.RowDefinitions>
<Grid RowSpacing="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="70" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Image Source="{Binding ContactImage}"
VerticalOptions="Center"
HorizontalOptions="Center"
HeightRequest="50" WidthRequest="50"/>
<Grid Grid.Column="1"
RowSpacing="1"
Padding="10,0,0,0"
VerticalOptions="Center">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="100" />
</Grid.ColumnDefinitions>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Label LineBreakMode="NoWrap"
TextColor="#474747"
Text="{Binding ContactName}">
</Label>
<Label LineBreakMode="NoWrap"
TextColor="#474747"
Grid.Row="1"
Text="{Binding ContactNumber}">
</Label>
</Grid>
<Button Grid.Column="1"
Text="Call"
Command="{Binding Source={RelativeSource AncestorType={x:Type ContentPage}}, Path=BindingContext.TapCommand}">
</Button>
</Grid>
<Grid Grid.Row="0"
Grid.Column="2"
RowSpacing="0"
HorizontalOptions="End" VerticalOptions="Start">
<Label LineBreakMode="NoWrap"
TextColor="#474747"
Text="{Binding ContactType}">
</Label>
</Grid>
</Grid>
</Grid>
</ViewCell.View>
</ViewCell>
C#: ViewModel Command definition
public ObservableCollection<Contacts> contactsinfo { get; set; }
public ContactsViewModel()
{
contactsinfo = new ObservableCollection<Contacts>();
TapCommand = new Command(OnTapped);
GenerateInfo();
}
private void OnTapped(object obj)
{
App.Current.MainPage.DisplayAlert("Message","Button tapped","Ok");
}