how to have 2 data binding fields in one Xamarin forms label?

*Update: With the release of Xamarin Forms 4.7, you can now use Multi-Bindings instead of creating a getter property. Using the first and last name example, you would do something like this:

<StackLayout Padding="20,0,0,0"  HorizontalOptions="CenterAndExpand" >
    <Label x:Name="FirstName">
        <Label.Text>
            <MultiBinding StringFormat="{}{0} {1}">
                <Binding Path="FirstName" />
                <Binding Path="LastName" />
            </MultiBinding>
        </Label.Text>
    </Label>
    .........
</StackLayout>

*Pre-Xamarin Forms 4.7 What I do in this situation is to put an extra property on the model that combines the two properties.

public class ContactInfo {
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string FirstLastName { get { return FirstName + " " + LastName; }}
    //Or use C# 6 goodness
    //public string FirstLastName => FirstName + " " + LastName;
}

Now in your ViewModel, if first or last name changes, you would need to do something like this to update the FirstLastName property:

private string _firstLastName;
public string FirstLastName {
    get { return _firstLastName; }
    set {
        if(_firstLastName != value) {
            _firstLastName = value;
            SetPropertyChanged();
        }
    }
}

private string _firstName;
public string FirstName {
    get { return _firstName; }
    set {
        if(_firstName != value) {
            _firstName = value;
            SetPropertyChanged();
            SetPropertyChanged("FirstLastName"); //Also send alert that FirstLastName changed
        }
    }
}

Then do the same for you LastName property.

Edit: Your XAML would then look like:

<StackLayout Padding="20,0,0,0"  HorizontalOptions="CenterAndExpand" >
    <Label x:Name="FirstName" Text="{Binding FirstLastName}"/>
    .....
</StackLayout>

Edit2: So since you are probably not ever changing the First or Last Name property while showing the UI, you just need to add the property to your model, like I show in the ContactInfo code above, and then change your label, like I show in the edit above and you will be good to go.

As Ed Phuket said it is working but :
You need to add Mode=OneWay if you want it to update with OnPropertyChanged event to the span because it has OneTime Binding mode as default