使用 Type 变量声明变量

Question

I have this code:

Type leftType = workItem[LeftFieldName].GetType();

I then want to declare a variable of that type:

leftType someVar;

Is that possible?

Answer 1

You can do something like these and cast them to a known interface.

var someVar = Convert.ChangeType(someOriginalValue, workItem[LeftFieldName].GetType());
var someVar = Activator.CreateInstance(workItem[LeftFieldName].GetType());

If you replace var with dynamic (and you are using .Net 4), you can call the methods you expect on the someVar object. If they don't exist, you'll just get a MissingMethodException.

Answer 2

This is not possible.

Variable types are a compile-time concept; it would make no sense to declare a variable of a type which is not known until runtime .
You wouldn't be able to do anything with the variable, since you wouldn't know what type it is.

You're probably looking for the dynamic keyword.

Answer 3

No, that is not possible. The type of a variable has to be known at compile time.

You can declare a variable of type object , it will be capable of storing any data type.

Answer 4

You cannot do that.

You could use the dynamic type for .Net 4, but for earlier .Net versions, the only type that will fit is object , which you will need to manually cast later by again testing .GetType() on what you assigned to the object -typed variable.

Reading: SO link: whats-the-difference-between-dynamicc-4-and-var

Answer 5

object x = Activator.CreateInstance(Type) will let you create the object. Whether you can do much with it beyond that point, I'm not sure.

Answer 6

GetType is evaluated at run-time, and non- dynamic declaration is at compile-time (it does get more specific than that, yes), so no. Even var will require you to assign a value to it that is of unambiguous type.