在XAML中使用数字类型资源

add to the head of the xamlfile

xmlns:System="clr-namespace:System;assembly=mscorlib"

Then Add to the resouce section:

<System:Double x:Key="theMargin">2.35</System:Double>

Last, use a thickness on the margin:

<Button Content="Next">
   <Button.Margin>
      <Thickness Top="{StaticResource theMargin}" Left="0" Right="0"
                  Bottom ="{StaticResource theMargin}" />
   </Button.Margin>
</Button>