How can a WPF UserControl inherit a WPF UserControl?

Question

The following WPF UserControl called DataTypeWholeNumber which works.

Now I want to make a UserControl called DataTypeDateTime and DataTypeEmail, etc.

Many of the Dependency Properties will be shared by all these controls and therefore I want to put their common methods into a BaseDataType and have each of these UserControls inherit from this base type.

However, when I do that, I get the error: Partial Declaration may not have different base classes.

So how can I implement inheritance with UserControls so shared functionality is all in the base class?

using System.Windows; using System.Windows.Controls;  namespace TestDependencyProperty827.DataTypes {     public partial class DataTypeWholeNumber : BaseDataType     {         public DataTypeWholeNumber()         {             InitializeComponent();             DataContext = this;              //defaults             TheWidth = 200;         }          public string TheLabel         {             get             {                 return (string)GetValue(TheLabelProperty);             }             set             {                 SetValue(TheLabelProperty, value);             }         }          public static readonly DependencyProperty TheLabelProperty =             DependencyProperty.Register("TheLabel", typeof(string), typeof(BaseDataType),             new FrameworkPropertyMetadata());           public string TheContent         {             get             {                 return (string)GetValue(TheContentProperty);             }             set             {                 SetValue(TheContentProperty, value);             }         }          public static readonly DependencyProperty TheContentProperty =             DependencyProperty.Register("TheContent", typeof(string), typeof(BaseDataType),             new FrameworkPropertyMetadata());           public int TheWidth         {             get             {                 return (int)GetValue(TheWidthProperty);             }             set             {                 SetValue(TheWidthProperty, value);             }         }          public static readonly DependencyProperty TheWidthProperty =             DependencyProperty.Register("TheWidth", typeof(int), typeof(DataTypeWholeNumber),             new FrameworkPropertyMetadata());        } } 

Answer 1

Ensure that you have changed the first tag in the xaml to also inherit from your new basetype

So

<UserControl x:Class="TestDependencyProperty827.DataTypes.DataTypeWholeNumber"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"             xmlns:s="clr-namespace:System;assembly=mscorlib"     > 

becomes

<myTypes:BaseDataType x:Class="TestDependencyProperty827.DataTypes.DataTypeWholeNumber"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"             xmlns:s="clr-namespace:System;assembly=mscorlib"     xmlns:myTypes="clr-namespace:TestDependencyProperty827.DataTypes"     > 

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So, to summarise the complete answer including the extra details from the comments below:

• The base class should not include a xaml file. Define it in a single (non-partial) cs file and define it to inherit directly from Usercontrol.
• Ensure that the subclass inherits from the base class both in the cs code-behind file and in the first tag of the xaml (as shown above).