通过在任何类之外声明的反射访问委托
本文关键字:反射 访问 声明 任何类 | 更新日期: 2023-09-27 18:09:18
我正在尝试一个反映的演示。我想在这门课上反映的程序集是这样的
namespace DelegatesSampleApplication
{
delegate bool IsPromotable (Employee employee); // Declaration Syntax is similar to that of a method's
class Program
{
public static void Main(string[] args)
{
//code goes here
}
}
class Employee
{
public int EmployeeId { get; set; }
public string EmployeeName { get; set; }
public int Salary { get; set; }
public int Experience { get; set; }
public void PromoteEmployees(List<Employee> employeeList, IsPromotable isPromotableObj)
{
/*foreach (Employee employee in employeeList)
{
if (employee.Experience >= 5 && employee.Salary >= 10000) //That's a hard-coded logic that you have developed as a Framework Developer which makes the class itself not reusable
{
Console.WriteLine(" {0} will be promoted in the next R.P. Cycle ", employee.EmployeeName);
}
}
Console.ReadKey();*/
foreach (Employee employee in employeeList)
{
if (isPromotableObj(employee))
{
Console.WriteLine(" {0} will be promoted in the next R.P. Cycle ", employee.EmployeeName);
}
}
Console.ReadKey();
}
}
}
现在我面临的问题是,我试图在我的程序中读取这个程序集,并试图调用在类实例中作为参数的委托。我要做的是在一个完全不同的类中执行类似的操作
namespace ReflectionSample
{
delegate bool empIsPromotable (Object obj);
class Program
{
static void Main(string[] args)
{
Console.WriteLine("***************Loading External assembly*************");
Assembly assembly = Assembly.LoadFrom(@"C:'Users'Chiranjib'Documents'visual studio 2012'Projects'DelegatesSampleApplication'DelegatesSampleApplication'bin'Debug'DelegatesSampleApplication.exe");
Type employeeType = assembly.GetType("DelegatesSampleApplication.Employee"); //Gets the System.Type object for the Employee Class from the just loaded assembly with all it's dependencies
Console.WriteLine("***************Loading External assembly properties*************");
//Setting properties here
Console.WriteLine("***************Creating an array list that will hold these employee instances***************");
List<Object> employeeInstanceList = new List<object>();
employeeInstanceList.Add(employeeInstance);
employeeInstanceList.Add(employeeInstance2);
Console.WriteLine("***************Invoking External assembly methods*************");
var args = new Object[] {
new List<employeeType>(),
(((employeeInstance) => { return true; }))
};
Console.ReadKey();
}
}
}
这会抛出错误。说employeeType缺少程序集引用。另外,我不能将lambda表达式转换为对象。我不能直接类型转换为(IsPromotable)对吧?我在用反射。所以我应该没有直接访问权限。
我如何能够通过反射访问委托?请帮我渡过难关。
IsPromotable
是不可调用的,它只是一个委托定义。把它想象成一个界面。它只是告诉你方法取什么和返回什么,但实际上并没有做任何事情。
你可以这样调用PromoteEmployees
:
PromoteEmployees(new List<Employee>, (employee) => { return employee.Name == "Rob"; });
任何与IsPromotable
签名匹配的方法都是该方法的有效参数(即,任何接受Employee
并返回bool
的方法)。你能详细说明一下你到底想做什么吗?
如果你只想要一个委托列表,你可以这样做:
GetType().Assembly.GetTypes().Where(t => t.IsSubClassOf(typeof(BaseDelegate)));
注意;这将只返回当前大会中的代表。您可以将其更改为:
typeof(Employee).GetTypes().Assembly.Where(t => t.IsSubClassOf(typeof(BaseDelegate)));
要获取程序集中所有可浇注到IsPromotable
的方法,可以这样做:
var delegateMethod = typeof(IsPromotable).GetMethod("Invoke");
var @params = delegateMethod.GetParameters();
var returnType = delegateMethod.ReturnType;
var matchingMethods = typeof(IsPromotable)
.Assembly
.GetTypes()
.SelectMany(t => t.GetMethods())
.Where(m => {
if (m.ReturnType != returnType)
return false;
var currParams = m.GetParameters();
if (currParams.Length != @params.Length)
return false;
for(var i = 0; i < currParams.Length;i++)
if (currParams[i] != @params[i])
return false;
return true;
});
要调用带有反射的方法,您可以这样做:
var args = new Object[] {
new List<Employee>(),
((IsPromotable)((emp) => { return true; }))
};
var value = employeeType.InvokeMember("PromoteEmployees", BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public, null, employeeInstance, args);
或者,你可以给它传递一个常规方法:
var args = new Object[] {
new List<Employee>(),
((IsPromotable)Test)
};
var value = employeeType.InvokeMember("PromoteEmployees", BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public, null, employeeInstance, args);
使用方法:
private bool Test(Employee emp)
{
return false;
}