C＃通用继承解决方法

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示例：

我想要从TextBox或RichTextBox派生的几个专用文本框，它们都是从TextBoxBase派生的：

class CommonFeatures< T> ：T其中T：TextBoxBase { // TextBox和RichTextBox大多数常用功能，例如 protected override OnTextChanged（TextChangedEventArgs e） { //使用像SelectAll（）这样的TextBoxBase属性/方法; $ / code $ / pre

然后

class SpecializedTB：CommonFeatures< TextBox> { //使用特定于TextBox的属性/方法 protected override void OnTextChanged（TextChangedEventArgs e） { ... base.OnTextChanged（e）; code

class SpecializedRTB：CommonFeatures< RichTextBox> { //使用特定于RichTextBox的方法/属性}

不幸

class CommonFeatures< T> ：T其中T：TextBoxBase

不能编译（不能从'T'派生，因为它是一个类型参数）。

有没有很好的解决方案？感谢。

解决方案

你真的需要 CommonFeatures 来自 TextBoxBase ？

一个简单的解决方法可能是使用聚合而不是继承。所以你会有这样的东西：

public class CommonFeatures< T>其中T：TextBoxBase { private T innerTextBox; 保护CommonFeatures< T>（T inner） { innerTextBox = inner; innerTextBox.TextChanged + = OnTextChanged; } public T InnerTextBox {get {return innerTextBox; }} protected void OnTextChanged（object sender，TextChangedEventArgs e） { ...做你的东西} }

像@oxilumin说的那样，如果你不需要 CommonFeatures 成为 TextBoxBase 。

Example:

I'd like to have several specialized textboxes that derive from either TextBox or RichTextBox, which both derive from TextBoxBase:

class CommonFeatures<T> : T where T : TextBoxBase { // lots of features common to the TextBox and RichTextBox cases, like protected override void OnTextChanged(TextChangedEventArgs e) { //using TextBoxBase properties/methods like SelectAll(); } }

and then

class SpecializedTB : CommonFeatures<TextBox> { // using properties/methods specific to TextBox protected override void OnTextChanged(TextChangedEventArgs e) { ... base.OnTextChanged(e); } }

and

class SpecializedRTB : CommonFeatures<RichTextBox> { // using methods/properties specific to RichTextBox }

Unfortunately

class CommonFeatures<T> : T where T : TextBoxBase

doesn't compile ("Cannot derive from 'T' because it is a type parameter").

Is there a good solution to this? Thanks.

解决方案

C# generics don't support inheritance from a parameter type.

Do you really need CommonFeatures to derive from TextBoxBase?

A simple workaround may be to use aggregation instead of inheritance. So that you would have something like this:

public class CommonFeatures<T> where T : TextBoxBase { private T innerTextBox; protected CommonFeatures<T>(T inner) { innerTextBox = inner; innerTextBox.TextChanged += OnTextChanged; } public T InnerTextBox { get { return innerTextBox; } } protected virtual void OnTextChanged(object sender, TextChangedEventArgs e) { ... do your stuff } }

Like @oxilumin says, extension methods may also be a great alternative if you don't really need CommonFeatures to be a TextBoxBase.