将动作委托作为参数传递给构造函数时出现参数错误 [英] Argument error while passing Action delegate as parameter to constructor

问题描述

我试图将Action委托传递给构造函数，但遇到以下错误：

I am trying to pass Action delegate with to constructor but getting below error :

Delegate'Action'不接受0参数

Delegate 'Action' does not take 0 arguments

代码：

public sealed class VariantProcessor
{
    private string _myAppConnectionString { get; set; }
    private readonly Action<Variant> _transform;
    public Variant(string _myAppConnectionString,Action<Variant> transform)
    {
         _myAppConnectionString = _myAppConnectionString;
         _transform = transform;
    }
    public void Process(Variant model)
    {
        try
        {
            _transform(model);
             //version creation shared by both the derived types
        }
        catch (Exception) 
        {
        }
    }
}

public class AggregateCalculator : IVariantProcessor
{
    private string _myAppConnectionString { get; set; }
     public void Process(Variant model)
     {
            _myAppConnectionString = ConfigurationManager.ConnectionStrings["dbConnectionString"].ConnectionString;
            new VariantProcessor( _myAppConnectionString,
               () => Transform(model) //error
               );
     }
    private void Transform(Variant model)
    {
        //logic on variant model
    }
}

我也尝试过这种方法，但还是没有运气：

I tried like this as well but still no luck :

new VariantProcessor(_myAppConnectionString,
                   Transform(model) // error
                    );

实际上我在理解此语法时遇到问题（）=> Transform（model）因此在这里我没有得到什么问题。

Actually I have problem understanding this syntax () => Transform(model) hence I am not getting whats the problem here.

有人可以帮我弄清楚这里有什么问题吗？

Can someone please help me figuring out whats the problem here ?

推荐答案

构造函数执行的动作是 Action< Variant> ，这意味着它是一段代码，它使用类型为 Variant 的单个参数并返回void（因为 Action 不返回任何内容。

The Action that your constructor takes is a Action<Variant> which means it is a piece of code that takes a single parameter of type Variant and returns void (because an Action doesn't return anything.

调用构造函数时，您可以传递一个带有单个参数的lambda像这样：

When you call the constructor you can either pass it a lambda that takes a single parameter like this:

new VariantProcessor(_myAppConnectionString, model => Transform(model));

或将其传递给采用 Variant 并返回 void ：

or you can pass it the name of a function that takes a Variant and returns void:

new VariantProcessor(_myAppConnectionString, Transform);

语法：

() => Transform(model)

表示一个带零参数的lambda（即（） ）表示。您需要提供一个包含单个参数的lambda。您可以将其编写为：

means a lambda that takes zero parameters (that's that the ()) means. You need to supply a lambda that takes a single parameter. You can write it either as:

model => Transform(model)

或

(model) => Transform(model)

当您拥有需要多个参数的lambda时，您必须放在括号内。

When you've got a lambda that takes more than one parameter then you have to put them inside brackets.

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