C＃-如何在“通用类”类型的MainForm类中声明变量而不指定通用类型

Question

I have the following generic class:

internal class AutoRegisterThread<T> where T: AutoRegisterAbstract
{
field1....
method1...
}

I have 5 classes that implement AutoRegisterAbstract (abstract class).

and in my Main form (internal partial class MainForm : Form), I need to declare a field :

AutoRegisterThread<> _currentThread

without specifying the generic type, because I may initiate _currentThread as:

_currentThread=new AutoRegisterThread<implementedClass1> 

or

_currentThread=new AutoRegisterThread<implementedClass2>

_currentThread: will be used across the Form (in many events)

Answer 1

When you have a generic class in C#, you have to provide the type parameter. You could write another class that would not be generic. If there is any logic, that should be shared between generic and non-generic classes, you can move that logic to one more new class.

Answer 2

Inherit from a non-generic base class:

internal abstract class AutoRegisterThreadBase { }

internal class AutoRegisterThread<T> : AutoRegisterThreadBase 
   where T: AutoRegisterAbstract
{
field1....
method1...
}

Your main form field can now be of type AutoRegisterThreadBase

Note, if desired, the non-generic parent class can have the same name as the generic class; in your case, AutoRegisterThread .

EDIT : Extended example, with usage:

internal abstract class AutoRegisterThreadBase { /* Leave empty, or put methods that don't depend on typeof(T) */ }
internal abstract class AutoRegisterAbstract { /* Can have whatever code you need */ }

internal class AutoRegisterThread<T> : AutoRegisterThreadBase
    where T : AutoRegisterAbstract
{
    private int someField;
    public void SomeMethod() { }        
}

internal class AutoRegisterWidget : AutoRegisterAbstract { /* An implementation of AutoRegisterAbstract; put any relevant code here */ }

// A type that stores an AutoRegisterThread<T> (as an AutoRegisterThreadBase)
class SomeType
{
    public AutoRegisterThreadBase MyAutoRegisterThread { get; set; }
}

// Your code that uses/calls the above types
class Program
{        
    static void Main(string[] args)
    {
        var someType = new SomeType();

        // Any sub-class of AutoRegisterThreadBase, including generic classes, is valid
        someType.MyAutoRegisterThread = new AutoRegisterThread<AutoRegisterWidget>();

        // You can then get a local reference to that type 
        // in the code that's created it - since you know the type here
        var localRefToMyAutoRegisterThread = someType.MyAutoRegisterThread as AutoRegisterThread<AutoRegisterWidget>;
        localRefToMyAutoRegisterThread.SomeMethod();
    }
}