使用类型变量转换对象 [英] cast object with a Type variable

问题描述

以下内容当然无效。有没有可能这样的方法呢？

  Type newObjectType = typeof（MyClass）; 
 
 var newObject =给定对象为newObjectType; 
  

解决方案

newObjectType 是 Type 类（包含有关该类型的元数据）的实例，而不是 type 本身。 / p>

这应该可行

  var newObject = namedObject as MyClass; 
  

OR

  var newObject =（MyClass）给定对象; 
  

由于编译时间，将类型强制转换为类型的实例确实没有任何意义>必须知道变量类型应该是什么，而类型的实例是运行时概念。

var 唯一可行的方法是在编译时知道变量的类型。

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UPDATE

通常，铸造是一个编译时概念，即您必须在编译时知道类型。

类型转换是运行时概念。

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UPDATE 2

如果您需要使用类型为变量的调用，并且在编译时不知道类型，则可以使用 reflection ：在类型实例上使用 MethodInfo 的 Invoke 方法。

  object myString = Ali; 
类型type = myString.GetType（）; 
 MethodInfo methodInfo = type.GetMethods（）。Where（m => m.Name == ToUpper）。First（）; 
对象被调用= methodInfo.Invoke（myString，null）; 
 Console.WriteLine（已调用）; 
 Console.ReadLine（）; 
  

The following doesn't work, of course. Is there a possible way, which is pretty similar like this?

Type newObjectType = typeof(MyClass);

var newObject = givenObject as newObjectType;

解决方案

newObjectType is an instance of the Type class (containing metadata about the type) not the type itself.

This should work

var newObject = givenObject as MyClass;

OR

var newObject = (MyClass) givenObject;

Casting to an instance of a type really does not make sense since compile time has to know what the variable type should be while instance of a type is a runtime concept.

The only way var can work is that the type of the variable is known at compile-time.

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UPDATE

Casting generally is a compile-time concept, i.e. you have to know the type at compile-time.

Type Conversion is a runtime concept.

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UPDATE 2

If you need to make a call using a variable of the type and you do not know the type at compile time, you can use reflection: use Invoke method of the MethodInfo on the type instance.

object myString = "Ali";
Type type = myString.GetType();
MethodInfo methodInfo = type.GetMethods().Where(m=>m.Name == "ToUpper").First();
object invoked = methodInfo.Invoke(myString, null);
Console.WriteLine(invoked);
Console.ReadLine();

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