Find Control Styles with FindResource()

   
  

<Window x:Class="ControlStyles.Window1"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="ControlStyles" Height="300" Width="300">
  <Window.Resources>
    <Style x:Key="StyleA">
      <Setter Property="Control.FontSize" Value="20" />
      <Setter Property="Control.FontWeight" Value="Bold" />
      <Setter Property="Control.BorderThickness" Value="2" />
    </Style>
    <Style x:Key="StyleB">
      <Setter Property="Control.FontSize" Value="10" />
      <Setter Property="Control.FontWeight" Value="Normal" />
      <Setter Property="Control.BorderThickness" Value="1" />
    </Style>

  </Window.Resources>

  <Grid>
    <Button Click="MyClickEvent"
      Style="{StaticResource StyleB}"
      VerticalAlignment="Top"
      HorizontalAlignment="Left"
      Grid.Column="0"
      Grid.ColumnSpan="1"
      Grid.Row="0"
      Grid.RowSpan="1"
      Margin="20"
      Width="75"
      Height="23"
      Name="btnGo">Go</Button>
  </Grid>
</Window>
//File:Window.xaml.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;


namespace ControlStyles
{
    public partial class Window1 : System.Windows.Window
    {
        public Window1()
        {
            InitializeComponent();
        }

        private void MyClickEvent(object sender, RoutedEventArgs e)
        {
            btnGo.Style = (Style)FindResource("StyleA");
        }
    }
}