C＃通用继承解决方法 [英] C# Generic Inheritance workaround

问题描述

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.

                        
这篇关于C＃通用继承解决方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！