Xamarin.Forms アプリでの実例を交えて C# のリフレクション機能周りについて簡単な紹介をします。 Xamarin や Xamarin.Forms の話と言うよりは C# (初〜中級者向け？)の話です。

2. 概要

3. 目次

5. reflectionとは？

6. reflectionとは？
自
己言及

8. BindableProperty

9. 素のBindableProperty
public class AlphaCircleImageCell : ViewCell
{
public static readonly BindableProperty ImageSourceProperty = BindableProperty.Create
(
nameof(ImageSource),
typeof(ImageSource),
typeof(AlphaCircleImageCell),
propertyChanged: (bindable, oldValue, newValue) => ((AlphaCircleImageCell)bindable).ImageSource = (ImageSource)newValue
);
public static readonly BindableProperty TextProperty = BindableProperty.Create
(
nameof(Text),
typeof(string),
typeof(AlphaCircleImageCell),
propertyChanged: (bindable, oldValue, newValue) => ((AlphaCircleImageCell)bindable).Text = (string)newValue
);
...
}

10. 素のBindableProperty
var Template = new DataTemplate(typeof(AlphaCircleImageCell));
Template.SetBinding(AlphaCircleImageCell.ImageSourceProperty, "AvatarUrl");
Template.SetBinding(AlphaCircleImageCell.TextProperty, "Login");
var List = new ListView
{
ItemTemplate = Template,
};

11. BindableProperty

12. BindableProperty

13. 簡潔なBindableProperty
必要ありません！
public class AlphaCircleImageCell : ViewCell
{
public static readonly BindableProperty ImageSourceProperty = BindableProperty.Create
(
nameof(ImageSource),
typeof(ImageSource),
typeof(AlphaCircleImageCell),
propertyChanged: (bindable, oldValue, newValue) => ((AlphaCircleImageCell)bindable).ImageSource = (ImageSource)newValue
);
public static readonly BindableProperty TextProperty = BindableProperty.Create
(
nameof(Text),
typeof(string),
typeof(AlphaCircleImageCell),
propertyChanged: (bindable, oldValue, newValue) => ((AlphaCircleImageCell)bindable).Text = (string)newValue
);
...
}

14. 簡潔なBindableProperty
public class AlphaCircleImageCell : ViewCell
{
public static readonly BindableProperty ImageSourceProperty =
typeof(AlphaCircleImageCell).GetRuntimeProperty("ImageSource").CreateBindableProperty();
public static readonly BindableProperty TextProperty =
typeof(AlphaCircleImageCell).GetRuntimeProperty("Text").CreateBindableProperty();
...
}

15. 簡潔なBindableProperty
var List = new ListView
{
ItemTemplate = new DataTemplateEx(typeof(AlphaCircleImageCell))
.SetBinding("ImageSource", "AvatarUrl")
.SetBinding("Text", "Login"),
};

16. 簡潔なBindableProperty
var List = new ListView
{
ItemTemplate = new DataTemplateEx(typeof(AlphaCircleImageCell))
.SetBindingList("ImageSource", "Text"),
};

17. BindableProperty

18. typeof 演算子
var AlphaCircleImageCellType = typeof(AlphaCircleImageCell);

19. Type.GetRuntimeProperty()
var ImageSourcePropertyInfo = typeof(AlphaCircleImageCell)
.GetRuntimeProperty("ImageSource");

20. PropertyInfo.SetValue()
typeof(AlphaCircleImageCell)
.GetRuntimeProperty("ImageSource")
.SetValue(ImageCell, IconImage); // ImageCell.ImageSource = IconImage; と等価

21. BindableProperty

22. BindableProperty のヘルパー
public static class BindablePropertyEx
{
public static BindableProperty CreateBindableProperty(this PropertyInfo PropertyInfo, object DefaultValue)
{
return BindableProperty.Create
(
PropertyInfo.Name,
PropertyInfo.PropertyType,
PropertyInfo.DeclaringType,
DefaultValue,
propertyChanged: (bindable, oldValue, newValue) => PropertyInfo.SetValue(bindable, newValue)
);
}
public static BindableProperty CreateBindableProperty(this PropertyInfo PropertyInfo)
{
return PropertyInfo.CreateBindableProperty
(
PropertyInfo.PropertyType.GetTypeInfo().IsValueType ?
Activator.CreateInstance(PropertyInfo.PropertyType) :
null
);
}
}

23. public class DataTemplateEx : DataTemplate
{
Type DeclaringType;
public DataTemplateEx(Type aDeclaringType)
:base(aDeclaringType)
{
DeclaringType = aDeclaringType;
}
public DataTemplateEx SetBinding(string ViewPropertyName, string DataPropertyName, object DefaultValue)
{
this.SetBinding
(
DeclaringType.GetRuntimeProperty(ViewPropertyName).CreateBindableProperty(DefaultValue),
DataPropertyName
);
return this;
}
public DataTemplateEx SetBinding(string ViewPropertyName, string DataPropertyName)
{
this.SetBinding
(
DeclaringType.GetRuntimeProperty(ViewPropertyName).CreateBindableProperty(),
DataPropertyName
);
return this;
}
public DataTemplateEx SetBindingList(params string[] PropertyNameList)
{
foreach(var PropertyName in PropertyNameList)
{
SetBinding
(
PropertyName,
PropertyName
);
}
return this;
}
}

25. 匿名クラス

26. 匿名クラス

27. 匿名クラス

28. 匿名クラス

29. 匿名クラス

30. 匿名クラス
var User = List.SelectedItem.GetValue<string>("Text");

31. PropertyInfo.GetValue()
var IconImage = typeof(AlphaCircleImageCell)
.GetRuntimeProperty("ImageSource")
.GetValue(ImageCell); // IconImage = ImageCell.ImageSource; と等価

32. 匿名クラス
static public class ValueEx
{
public static T GetValue<T>(this object o, string name)
{
return (T)o.GetType().GetRuntimeProperty(name).GetValue(o);
}
}

33. 匿名クラス

35. 既知の問題