xamarin forms get a value from ResourceDictionary - xamarin.forms

Question

I have 2 different values for the Left Margin and the Right Margin for my application. (Let say 27 and 64)
Is it possible to get these values from the ResourcesDictionaty and set them in my XAML.
For example
<StackLayout Margin="{Left1},0,{Right1},0">
</StackLayout>

Answer 1

You can specify them as double values in ResourceDictionary and refer to them in other resources/styles or at element level itself.
Sample resource-dictionary
<ResourceDictionary>
<!-- namespace declaration
xmlns:sys="clr-namespace:System;assembly=System.Runtime" -->
<sys:Double x:Key="leftMargin">20</sys:Double>
<sys:Double x:Key="rightMargin">30</sys:Double>
<Thickness x:Key="MyMargin1"
Left="{StaticResource leftMargin}"
Right="{StaticResource rightMargin}"
Top="20"
Bottom="30" />
<Thickness x:Key="MyMargin2"
Left="{StaticResource leftMargin}"
Right="{StaticResource rightMargin}"
Top="5"
Bottom="15" />
</ResourceDictionary>
Sample usage
<StackLayout>
<BoxView BackgroundColor="Blue" Margin="{StaticResource MyMargin1}" />
<BoxView HeightRequest="1" BackgroundColor="Black" />
<BoxView BackgroundColor="Red" Margin="{StaticResource MyMargin2}" />
<BoxView HeightRequest="1" BackgroundColor="Black" />
<BoxView BackgroundColor="Yellow">
<BoxView.Margin>
<Thickness
Left="{StaticResource leftMargin}"
Right="{StaticResource rightMargin}"
Top="30"
Bottom="10" />
</BoxView.Margin>
</BoxView>
<BoxView HeightRequest="1" BackgroundColor="Black" />
</StackLayout>

Answer 2

I don't think doing this for individual values will work. You can however bind the entire Margin to a value in a resource dictionary as follows:
<ResourceDictionary>
<Thickness x:Key="MyMargin">27,0,64,0</Thickness>
</ResourceDictionary>
<StackLayout Margin="{StaticResource MyMargin}">
</StackLayout>