C# 如何从对象中获取值但其类型无法访问
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How to get value from the object but its type is unreachable
提问by jojo
For instance, in my current class, there is a hashtable,
例如，在我当前的班级中，有一个哈希表，
Hashtable t = GetHashable(); //get from somewhere.
var b = t["key"];
the type of b is hidden from my current class, it is unreachable, not a public class type.
b 的类型对我当前的类是隐藏的，它无法访问，而不是公共类类型。
but i want to get a value from b, for example b has a field call "ID", i need to get the ID from b.
但我想从 b 获取一个值，例如 b 有一个字段调用“ID”，我需要从 b 获取 ID。
is there anyway i can get it, reflection ???
无论如何我可以得到它，反思？？？
采纳答案by Reed Copsey
If you don't know the type, then you'll need reflection:
如果你不知道类型，那么你需要反射：
object b = t["key"];
Type typeB = b.GetType();
// If ID is a property
object value = typeB.GetProperty("ID").GetValue(b, null);
// If ID is a field
object value = typeB.GetField("ID").GetValue(b);
回答by Charles Bretana
By unreachable, you mean not a publically instantiable type? Cause if the assembly that defines this type is not there, then the object itself could not be fetched, the compiler would throw an error.
无法访问，您的意思是不是可公开实例化的类型？因为如果定义此类型的程序集不存在，则无法获取对象本身，编译器将抛出错误。
So, if the assembly defining the type is there, then yes you can use reflection to get at it...
因此，如果定义类型的程序集在那里，那么是的，您可以使用反射来获取它...
回答by Marc Gravell
In C# 4.0, this would just be:
在 C# 4.0 中，这将是：
dynamic b = t["key"];
dynamic id = b.ID; // or int if you expect int
Otherwise; reflection:
除此以外; 反射：
object b = t["key"];
// note I assume property here:
object id1 = b.GetType().GetProperty("ID").GetValue(b, null);
// or for a field:
object id2 = b.GetType().GetField("ID").GetValue(b);
Another easier approach is to have the type implement a common interface:
另一种更简单的方法是让类型实现一个公共接口：
var b = (IFoo)t["key"];
var id = b.ID; // because ID defined on IFoo, which the object implements
回答by Hardeep Singh
Just Try :
你试一试 ：
DataSet ds = (DataSet)OBJ;
Int32 MiD = Convert.ToInt32(ds.Tables[0].Rows[0]["MachineId"]);
