Disable autocomplete in Xamarin.Forms PCL XAML Page

While there's already an answer, I thought I'd elaborate a bit further about usage in XAML.

Unlike in code-behind, you cannot create a new instance of the Keyboard class to be used, but there IS a way. Hopefully you're already xaml-ified your App.cs (remove it, and create App.xaml and App.xaml.cs), that way you don't have to check if the Resources property has been initialized yet.

The next step is to override the OnStart() method, and add the proper entries for the various keyboards you use. I usually use three keyboards: numeric, e-mail and text. Another useful one is the Url keyboard, but you can add it the same way.

protected override void OnStart()
{
    base.OnStart();
    this.Resources.Add("KeyboardEmail", Keyboard.Email);
    this.Resources.Add("KeyboardText", Keyboard.Text);
    this.Resources.Add("KeyboardNumeric", Keyboard.Numeric);
}

This little code will make the keyboards available as static resources. To use them in XAML, just do the following:

<Entry x:Name="emailEntry" Text="{Binding EMail}" Keyboard="{StaticResource KeyboardEmail}" />

And voilá, your entry now has an e-mail keyboard.

Custom Keyboard instances can be created in XAML using the x:FactoryMethod attribute. What you're wanting can be achieved with the following markup:

<Entry Text="{Binding Code}" Placeholder="Code">
  <Entry.Keyboard>
    <Keyboard x:FactoryMethod="Create">
      <x:Arguments>
        <KeyboardFlags>None</KeyboardFlags>
      </x:Arguments>
    </Keyboard>
  </Entry.Keyboard>
</Entry>

KeyboardFlags.None removes all special keyboard features from the field.

Multiple enums can be specified in XAML by separating them with a comma:

<KeyboardFlags>CapitalizeSentence,Spellcheck</KeyboardFlags>

When you don't need a custom Keyboard, you can use one of the predefined ones by taking advantage of the x:Static attribute:

<Entry Placeholder="Phone" Keyboard="{x:Static Keyboard.Telephone}" />