可选参数，'Employee'的重载不会匹配委托'System.Func< Employee> [英] Optional Parameters, No overload for 'Employee' matches delegate 'System.Func<Employee>

问题描述

当试图调用一个引用带有可选参数的函数的委托时，iam获得
'Employee'匹配没有重载委托'System.Func

然后如何调用它，当我不需要传递参数时。

  Func< Employee> print =员工; 
 Employee employee = print（）; 
 
私人雇员雇员（int employeeID = 1）
 {
 return new Employee（）; 
 
  

解决方案

可选参数不包含更改方法签名。您试图将一个参数的方法转换为不带参数的委托 - 它们不兼容。

您可以使用一个lambda来委托您的方法使用可选参数的默认值：

  Func< Employee> print =（）=>雇员（）; 
 Employee employee = print（）; 
  

When trying to invoke a delegate which reference a function with optional parameter, iam getting No overload for 'Employee' matches delegate 'System.Func

Then how to call it, when i don't need to pass the parameter.

    Func<Employee> print = Employee;
    Employee employee = print();

    private Employee Employee(int employeeID = 1)
    {
        return new Employee();
    }

解决方案

The optional parameter doesn't change the method signature. You are trying to convert a method with one parameter to a delegate with no parameters - they are not compatible.

You can use a lambda that will delegate to your method making use of the default value for the optional parameter:

Func<Employee> print = () => Employee();
Employee employee = print();

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