CODEWITHSUNDEEP
c#.netreflectiontypes
Joshua Enfield
Joshua Enfield

Reputation: 18278

How can I pass a type, rather than an instance, to a function in C#?

I am attempting to use reflection to enumerate class fields and methods in order to do some automation in a web application. I am also abstracting this so that I could pass in any class.

Is there a way I could somehow pass in the type directly to a function to enumerate on rather than an instance of the type?

I would like the caller side to look like this:

var m = new MyClass(AClassOfSomeTypeIDefined);

I would like to avoid creating an instance as that is misleading to anyone who might use the class (as the instance isn't directly used).

Upvotes: 0

Views: 306

Answers (3)

John K
John K

Reputation: 28869

using System;

public void UseType(Type t) {
    // do something with t using reflection techniques - e.g.
    Console.WriteLine("compat with int? {0}", typeof(int).IsAssignableFrom(t));
}

Call it with C# typeof keyword and the data type you want to pass.

// Examples...
UseType( typeof(int) );
UseType( typeof(System.Int32) );
UseType( typeof(System.Windows.Controls.Button) );
UseType( typeof(IDisposable) );
UseType( typeof(WhateverTypeYouWant) );

System.Type is one of the cornerstones of reflection as you already know, so run with it.

Other notes
Depending on what you want to do with the type, the following peripheral details might be useful.

To create an instance of a Type at runtime without having used the new keyword at compile time, use the System.Activator class. e.g.

// Create a List of strings like: new List<string>();
var list = (List<string>) Activator.CreateInstance( typeof(List<string>) );

Upvotes: 3

Adam Robinson
Adam Robinson

Reputation: 185613

You can pass a Type object just like any other parameter.

class MyClass
{
    public MyClass(Type yourType)
    {
        // do as you please with yourType
    }
}

The call it:

var m = new MyClass(typeof(YourType));

Upvotes: 1

BrokenGlass
BrokenGlass

Reputation: 160852

yes just use the Type of your class. There's two basic ways to get the type:

Foo foo = new Foo();
Type myType = foo.GetType();
Type myTyp2 = typeof(Foo);

You can use GetType() if you only know the type at runtime (more common with reflection), or typeof() if you know the type at compile time already.

In your example this would be i.e.

var m = new MyClass(typeof(Foo));

Upvotes: 1

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