为什么DataTemplate返回类名而不是控件？

我想创建自定义控件添加属性Info和InfoTemplate .
我使用ContetnPresenter for Info属性在generic.xaml中定义ControlTemplate .
当我没有't use InfoTemplate it' s工作正常，但当我应用ItemTemplate时，内容表示为类名字符串 . 同样的模板应用于GroupBox工作就像预期的那样 . 我错了什么？我在OnApplyTemplate中需要一些额外的代码？
贝娄是我的应用程序和来源的打印屏幕 . 红色边框是GroupBox，蓝色是我的Control . 绿色边框是DataTemplate的一部分 .

EDIT: 为了测试我创建了MyGroupBox类，继承了GroupBox的形式并重写方法OnHeaderChanged

public class MyGroupBox : GroupBox
{
    protected override void OnHeaderChanged(object oldHeader, object newHeader)
    {
        //base.OnHeaderChanged(oldHeader, newHeader);
    }
}

在那种情况下，GroupBox.Heder的行为类似于我的MyCustomControl并显示文本而不是控件 . 所以问题是：我应该在我的控制事件中实现什么才能像我想要的那样工作？

MyCustomControl.cs

using System.Windows;
using System.Windows.Controls;

namespace WpfApplication7
{

    public class MyCustomControl : ContentControl
    {
        static MyCustomControl()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(MyCustomControl), new FrameworkPropertyMetadata(typeof(MyCustomControl)));
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
        }

        public object Info
        {
            get { return (object)GetValue(InfoProperty); }
            set { SetValue(InfoProperty, value); }
        }

        public DataTemplate InfoTemplate
        {
            get { return (DataTemplate)GetValue(InfoTemplateProperty); }
            set { SetValue(InfoTemplateProperty, value); }
        }

        public static readonly DependencyProperty InfoProperty =
            DependencyProperty.Register(nameof(Info), typeof(object), typeof(MyCustomControl), new PropertyMetadata(null));

        public static readonly DependencyProperty InfoTemplateProperty =
            DependencyProperty.Register(nameof(InfoTemplate), typeof(DataTemplate), typeof(MyCustomControl), new PropertyMetadata(null));
    }
}

Generic.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication7">

    <Style TargetType="{x:Type local:MyCustomControl}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:MyCustomControl}">
                    <StackPanel>

                        <TextBlock FontWeight="Bold">Info</TextBlock>
                        <ContentPresenter ContentSource="Info"/>

                        <TextBlock FontWeight="Bold">Content</TextBlock>
                        <ContentPresenter/>
                    </StackPanel>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

MainWindow.xml

<Window x:Class="WpfApplication7.MainWindow"
        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:local="clr-namespace:WpfApplication7"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Window.DataContext>
        DATA_CONTEXT
    </Window.DataContext>
    <Window.Resources>
        <DataTemplate x:Key="dataTemplate">
            <Border BorderBrush="Green" BorderThickness="5">
                <ContentPresenter Content="{Binding}"/>
            </Border>
        </DataTemplate>
    </Window.Resources>
    <StackPanel>

        <Border BorderBrush="Red" BorderThickness="4">
            <GroupBox HeaderTemplate="{StaticResource dataTemplate}">
                <GroupBox.Header>
                    <TextBlock Text="{Binding}"/>
                </GroupBox.Header>
            </GroupBox>
        </Border>

        <Border BorderBrush="Blue" BorderThickness="4">
            <local:MyCustomControl InfoTemplate="{StaticResource dataTemplate}">
                <local:MyCustomControl.Info>
                    <TextBlock Text="{Binding}"/>
                </local:MyCustomControl.Info>

                My content
            </local:MyCustomControl>
        </Border>
    </StackPanel>
</Window>

MainWindow.xaml.cs

using System.Collections.Generic;
using System.Windows;


namespace WpfApplication7
{

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }
}