指定委托参数的特定类型

Question

假设我有以下代表

public delegate void ControlInitializer(Control control);

有没有办法在指定委托时指定输入参数是什么类型的控件？例如

代替

ControlInitializer one = c => ((TextBox)c).Text = "Init Value"
ControlInitializer two = c => ((DropDownList)c).SelectedValue= "-1"

我能做点什么吗

ControlInitializer one = (TextBox c) => c.Text = "Init Value"
ControlInitializer two = (DropDownList c) => c.SelectedValue= "-1"

在这种情况下,Textbox是Control的子类吗？

更新:我还需要将这两个ControlInitialiser委托存储在例如

Dictionary<string, ControlInitializer>

将指定

Dictionary<string, ControlInitializer<Control>>

在这种情况下工作,因为我似乎无法让它工作.

提前致谢.

Answer 1

您可以使委托通用:

public delegate void ControlInitializer<TControl>(TControl control)
    where TControl : Control;

然后像这样使用它:

ControlInitializer<TextBox>      one = c => c.Text = "Init Value";
ControlInitializer<DropDownList> two = c => c.SelectedValue = "-1";

我想你的目标是这样的:

var init = new Init();

init.RegisterInitializer<TextBox>(c => c.Text = "Init Value");
init.RegisterInitializer<DropDownList>(c => c.SelectValue = "-1");

foreach (var c in Controls)
{
    init.ApplyInitializer(c);
}

由于David B回答中提到的原因,这有点困难.但是,你可以做的是隐藏抽象背后的类型,如下所示:

public class Init
{
    private readonly Dictionary<Type, Action<Control>> initializers;
    ...

    public void RegisterInitializer<TControl>(Action<TControl> i)
        where T Control : Control
    {
        initializers.Add(typeof(TControl), c => i((TControl)c));
    }

    public void ApplyInitializer(Control c)
    {
       initializers[c.GetType()](c);
    }
}