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WPF Control Factory

, 20 Apr 2010 CPOL
This article explains some advantages and disadvantages of factories, and shows one to use for generating WPF Controls.
WpfControlsAndSample.zip
WpfControlsAndSample
Pfz.ClassLibraries
Pfz
Caching
Collections
DataTypes
Extensions
Pfz.snk
Properties
Ranges
Threading
Pfz.WpfControls
BoundGridParts
Extensions
Pfz.WpfControls.snk
Properties
TypeConverters
WpfControlFactorySample
bin
Debug
Pfz.dll
Pfz.WpfControls.dll
WpfControlFactorySample.exe
Properties
Settings.settings
WpfControlFactorySample.suo
using System;
using System.Reflection;
using System.Windows;
using Pfz.Collections;
using Pfz.DataTypes;

namespace Pfz.WpfControls
{
	/// <summary>
	/// The heart of Pfz.WpfControls and Pfz.WpfControls.
	/// This factory allows you to register IValueContainer controls, so
	/// whenever you need a control for a specific type, the right control
	/// will be created.
	/// </summary>
	public static class ControlFactory
	{
		private static TypeDictionary<ConstructorInfo> fTypeDictionary = new TypeDictionary<ConstructorInfo>();
		
		/// <summary>
		/// Registers the default controls that came with Pfz.WpfControls.
		/// </summary>
		static ControlFactory()
		{
			Register<StringControl>();
			Register<DateControl>();
			Register<TimeControl>();
			Register<DateTimeControl>();
			Register<BooleanControl>();
			Register<PasswordControl>();
			Register<EnumControl>(true);
			p_Register(typeof(RangeControl<>), true);
		}
		
		/// <summary>
		/// Registers a control by it's type.
		/// </summary>
		public static void Register<T>()
		where
			T: UIElement, IValueContainer, IValueControl, new()
		{
			Register<T>(false);
		}
		
		/// <summary>
		/// Registers a control by it's type and allows you to tell if
		/// sub-types of the data-types supported by this control can
		/// use this control if a better one does not exist.
		/// </summary>
		public static void Register<T>(bool canGenerateForSubtypes)
		where
			T: UIElement, IValueContainer, IValueControl, new()
		{
			p_Register(typeof(T), canGenerateForSubtypes);
		}

		/// <summary>
		/// Registers a control by it's type and allows you to tell if
		/// sub-types of the data-types supported by this control can
		/// use this control if a better one does not exist.
		/// </summary>
		public static void Register(Type type, bool canGenerateForSubtypes)
		{
			if (type == null)
				throw new ArgumentNullException("type");
			
			if (!type.IsSubclassOf(typeof(UIElement)))
				throw new ArgumentException("type must be a sub-class of UIElement.", "type");
			
			if (!typeof(IValueControl).IsAssignableFrom(type))
				throw new ArgumentException("type must implement IDataControl.", "type");
			
			if (type.GetConstructor(Type.EmptyTypes) == null)
				throw new ArgumentException("type must have a public default constructor", "type");
			
			p_Register(type, canGenerateForSubtypes);
		}
		private static void p_Register(Type type, bool canGenerateForSubtypes)
		{
			bool added = false;
			Type[] interfaceTypes = type.GetInterfaces();
			foreach(var interfaceType in interfaceTypes)
			{
				if (!interfaceType.IsGenericType)
					continue;
				
				if (interfaceType.GetGenericTypeDefinition() != typeof(IValueContainer<>))
					continue;
				
				added = true;
				var dataType = interfaceType.GetGenericArguments()[0];
				
				if (dataType.IsGenericParameter)
				{
					var constraints = dataType.GetGenericParameterConstraints();
					if (constraints.Length == 0)
						dataType = typeof(object);
					else
						dataType = constraints[0];
				}
				
				ConstructorInfo constructorInfo = type.GetConstructor(Type.EmptyTypes);
				fTypeDictionary.Set(dataType, constructorInfo, canGenerateForSubtypes);
			}
			
			if (!added)
				throw new ArgumentException("controlType must implement IValueContainer<> for at least one type.");
		}
		
		/// <summary>
		/// Tries to create a control for the given data-type.
		/// The result can be null if there is not a control appropriate for the
		/// data-type.
		/// </summary>
		public static UIElement TryCreate(Type dataType)
		{
			if (dataType == null)
				throw new ArgumentNullException("dataType");
			
			ConstructorInfo constructorInfo = fTypeDictionary.FindUpOrDefault(dataType);
			if (constructorInfo == null)
				return null;
			
			Type declaringType = constructorInfo.DeclaringType;
			if (declaringType.ContainsGenericParameters)
			{
				Type madeType = declaringType.MakeGenericType(dataType);
				constructorInfo = madeType.GetConstructor(Type.EmptyTypes);
			}
			
			UIElement result = (UIElement)constructorInfo.Invoke(null);
			
			IHasPreferredDataType preferredDataType = result as IHasPreferredDataType;
			if (preferredDataType != null)
				preferredDataType.PreferredDataType = dataType;
			
			return result;
		}
		
		private static readonly MethodInfo fTypedTryCreate = typeof(ControlFactory).GetMethod("TryCreate", new Type[]{typeof(string)});
		/// <summary>
		/// Tries to create a control for the given data-type using the given
		/// displayName. If the control does not support displayName, a 
		/// LabellerControl will be created for it.
		/// The result can be null if there is no editor for the given data-type.
		/// </summary>
		public static UIElement TryCreate(Type dataType, string displayName)
		{
			if (dataType == null)
				throw new ArgumentNullException("dataType");
				
			UIElement result = TryCreate(dataType);
			
			if (result == null)
				return null;
			
			if (displayName != null)
			{
				IHasDisplayName hasDisplayName = result as IHasDisplayName;
				if(hasDisplayName != null)
					hasDisplayName.DisplayName = displayName;
				else
					result = new LabellerControl(result, displayName);
			}
			
			return result;
		}
	}
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Paulo Zemek
Engineer
United States United States
I started to program computers when I was 11 years old, as a hobbist, programming in AMOS Basic and Blitz Basic for Amiga.
At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0).
Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods.
 
At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do they work easier, faster and with less errors.
 
Now I just started working as a Senior Software Engineer at Microsoft.
 
Want more info or simply want to contact me?
Take a look at: http://paulozemek.azurewebsites.net/
Or e-mail me at: paulozemek@outlook.com
 
Codeproject MVP 2012
Microsoft MVP 2013-2014

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