一个自定义FrameworkElement的例子

class：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Controls;
using System.Windows;
using System.Windows.Media;

namespace WpfApplication25
{
    public class MyTextBlock : FrameworkElement
    {
        TextBlock t;
        public MyTextBlock()
        {
            t = new TextBlock() 
            {
                Text = "TextTextText",
                Background = Brushes.Blue,
                Width = 60,
                Height = 30
            };
            AddLogicalChild(t);
            AddVisualChild(t);
        }

        protected override Size MeasureOverride(Size availableSize)
        {
            t.Measure(availableSize);
            return base.MeasureOverride(availableSize);
        }

        protected override Size ArrangeOverride(Size finalSize)
        {
            t.Arrange(new Rect(new Point(50, 50), t.DesiredSize));
            return base.ArrangeOverride(finalSize);
        }

        // In order for the visual tree to be enumerated correctly,
        // we must override the GetVisualChild and VisualChildrenCount.
        protected override Visual GetVisualChild(int index)
        {
            return t;
        }

        protected override int VisualChildrenCount
        {
            get
            {
                return 1;
            }
        }
    }
}
Xaml ：

<Window x:Class="WpfApplication25.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300"
        xmlns:local="clr-namespace:WpfApplication25">
    <Grid>
        <local:MyTextBlock></local:MyTextBlock>
    </Grid>
</Window>