如何从后面的代码修改资源的属性？

Question

I've created an user control element which has a button with an individual style.
Inside this style I have a rectangle called "Rectangle".
Now i want to change the visibility of this rectangle from the code behind.
How can I do this?
Or in general: How can I change any of the properties of the resources from the code behind?

Button_Field.xaml

<UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:ed="http://schemas.microsoft.com/expression/2010/drawing"
    mc:Ignorable="d"
    x:Class="WpfControlLibrary_Battleship.Button_Field"
    x:Name="UserControl"
    d:DesignWidth="512" d:DesignHeight="512" Width="Auto" Height="Auto">
    <UserControl.Resources>
        <Style x:Key="ButtonStyle_FieldWater" TargetType="{x:Type Button}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Button}">
                        <Grid x:Name="Grid">
                            <Grid.RowDefinitions>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                                <ColumnDefinition/>
                            </Grid.ColumnDefinitions>
                            <Grid.Background>
                                <ImageBrush ImageSource="Images/Water.jpg"/>
                            </Grid.Background>
                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualStateGroup.Transitions>
                                        <VisualTransition From="MouseOver" GeneratedDuration="0">
                                            <Storyboard>
                                                <DoubleAnimation Duration="0:0:0.5" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_1"/>
                                                <DoubleAnimation Duration="0:0:0.5" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_2"/>
                                                <DoubleAnimation Duration="0:0:0.5" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_3"/>
                                                <DoubleAnimation Duration="0:0:0.5" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_4"/>
                                            </Storyboard>
                                        </VisualTransition>
                                    </VisualStateGroup.Transitions>
                                    <VisualState x:Name="Normal"/>
                                    <VisualState x:Name="MouseOver">
                                        <Storyboard>
                                            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_1">
                                                <EasingDoubleKeyFrame KeyTime="0" Value="1"/>
                                            </DoubleAnimationUsingKeyFrames>
                                            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_2">
                                                <EasingDoubleKeyFrame KeyTime="0" Value="1"/>
                                            </DoubleAnimationUsingKeyFrames>
                                            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_3">
                                                <EasingDoubleKeyFrame KeyTime="0" Value="1"/>
                                            </DoubleAnimationUsingKeyFrames>
                                            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Path_4">
                                                <EasingDoubleKeyFrame KeyTime="0" Value="1"/>
                                            </DoubleAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>
                                    <VisualState x:Name="Pressed"/>
                                    <VisualState x:Name="Disabled"/>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>
                            <Path x:Name="Path_1" Data="M2.5,2.5 L82.833332,2.5 M2.5000006,2.5 L2.5000006,82.833329" HorizontalAlignment="Stretch" Height="Auto" Margin="0" StrokeStartLineCap="Square" Stretch="Fill" StrokeEndLineCap="Square" Stroke="#FF9B0000" StrokeThickness="5" VerticalAlignment="Stretch" Width="Auto" Grid.ColumnSpan="2" Grid.RowSpan="2" Opacity="0"/>
                            <Path x:Name="Path_2" Grid.Column="6" Data="M2.5,2.5 L82.833356,2.5 M82.833333,2.5 L82.833333,82.833335" HorizontalAlignment="Stretch" Height="Auto" Margin="0" StrokeStartLineCap="Square" Stretch="Fill" StrokeEndLineCap="Square" Stroke="#FF9B0000" StrokeThickness="5" VerticalAlignment="Stretch" Width="Auto" Grid.ColumnSpan="2" Grid.RowSpan="2" Opacity="0"/>
                            <Path x:Name="Path_3" Data="M2.5,2.5 L2.5,82.833328 M2.5,82.833323 L82.833336,82.833323" HorizontalAlignment="Stretch" Margin="0" Grid.Row="6" StrokeStartLineCap="Square" Stretch="Fill" StrokeEndLineCap="Square" Stroke="#FF9B0000" StrokeThickness="5" Width="Auto" Grid.ColumnSpan="2" Grid.RowSpan="2" Opacity="0"/>
                            <Path x:Name="Path_4" Grid.Column="6" Data="M2.5000001,168.16667 L168.16665,168.16667 M168.16666,2.5000051 L168.16666,168.1667" HorizontalAlignment="Stretch" Height="Auto" Margin="0" Grid.Row="6" StrokeStartLineCap="Square" Stretch="Fill" StrokeEndLineCap="Square" Stroke="#FF9B0000" StrokeThickness="5" VerticalAlignment="Stretch" Width="Auto" Grid.ColumnSpan="2" Grid.RowSpan="2" Opacity="0"/>
                            <Rectangle x:Name="Rectangle" Grid.ColumnSpan="8" Fill="Red" Margin="0" Grid.RowSpan="8" Stroke="Black" Opacity="0.495">
                                <Rectangle.Visibility>
                                    <Visibility>Hidden</Visibility>
                                </Rectangle.Visibility>
                            </Rectangle>
                        </Grid>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsFocused" Value="True"/>
                            <Trigger Property="IsDefaulted" Value="True"/>
                            <Trigger Property="IsMouseOver" Value="True"/>
                            <Trigger Property="IsPressed" Value="True"/>
                            <Trigger Property="IsEnabled" Value="False"/>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>

    <Button x:Name="Button" Content="Button" Style="{DynamicResource ButtonStyle_FieldWater}"/>
</UserControl>

Button_Field.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.Navigation;
using System.Windows.Shapes;
using Battleship_LOGIC;

namespace WpfControlLibrary_Battleship
{
    /// <summary>
    /// Interaktionslogik für Button_Field.xaml
    /// </summary>
    public partial class Button_Field : UserControl
    {
        private Battleship_LOGIC.Game_Logic.Point _point;

        public Button_Field(Battleship_LOGIC.Game_Logic.Point point)
        {
            InitializeComponent();
            _point = point;
        }

        public void redBackground()
        {
            //Set Visibility of Rectangle to "Visible"
        }

        public Battleship_LOGIC.Game_Logic.Point Point
        {
            get { return _point; }
        }
    }
}

Answer 1

Try this:

var rect = (Rectangle)Button.Template.FindName("Rectangle", Button);
rect.Visibility = System.Windows.Visibility.Visible;