<Window x:Class="exSplitter.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <!--GridSplitter样式-->
        <Style x:Key="GridSplitterPreviewStyle">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Rectangle Fill="#80000000"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <Style x:Key="GridSplitterStyle1" TargetType="{x:Type GridSplitter}">
            <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
            <Setter Property="PreviewStyle" Value="{StaticResource GridSplitterPreviewStyle}"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type GridSplitter}">
                        <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}">
                                <Button Name="btnExpend"  Content=":" VerticalAlignment="Center" Height="50" Panel.ZIndex="0" Cursor="Hand"/>
                            </Grid>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>
    <Grid Name="grdWorkbench">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="0.282*"/>
            <ColumnDefinition Width="6"/>
            <ColumnDefinition Width="0.718*"/>
        </Grid.ColumnDefinitions>
        <Grid Name="grd1"  Margin="0" Background="#FFD8D8D8"/>
        <GridSplitter x:Name="gsSplitterr" Grid.Column="1" HorizontalAlignment="Stretch" Margin="0" Background="#FF9F9F9F" Style="{DynamicResource GridSplitterStyle1}"/>
        <Grid Name="grd2"  Grid.Column="2" Margin="5,0,-5,0" Background="#FFEBF5F7"/>
    </Grid>
</Window>

后台代码：

using System;
using System.Collections.Generic;
using System.Linq;
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;
namespace exSplitter
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
        GridLength m_WidthCache;
        public MainWindow()
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(MainWindow_Loaded);
        void MainWindow_Loaded(object sender, RoutedEventArgs e)
            //获取GridSplitterr的cotrolTemplate中的按钮btn，必须在Loaded之后才能获取到
            Button btnGrdSplitter = gsSplitterr.Template.FindName("btnExpend", gsSplitterr) as Button;
            if (btnGrdSplitter != null)
                btnGrdSplitter.Click += new RoutedEventHandler(btnGrdSplitter_Click);
        void btnGrdSplitter_Click(object sender, RoutedEventArgs e)
            GridLength temp = grdWorkbench.ColumnDefinitions[0].Width;
            GridLength def = new GridLength();
            if (temp.Equals(def))
                //恢复
                grdWorkbench.ColumnDefinitions[0].Width = m_WidthCache;
                //折叠
                m_WidthCache = grdWorkbench.ColumnDefinitions[0].Width;
                grdWorkbench.ColumnDefinitions[0].Width = def;
 代码：https://files.cnblogs.com/kooleven/exSplitter.rar