Typeof. The C# typeof operator returns Type objects. It is often used as a parameter or as a variable or field. It is part of an expression that acquires the Type pointer.

Type

Reflection

Some methods, like Enum.Parse, require a Type object, and typeof can get us this object. We use the typeof operator to get more information about a class.

sizeof

nameof

Typeof example. Here we use typeof in a simple program. The types the program uses are found in the System namespace and the System.IO namespace.

Console.WriteLine

using System;
using System.IO;

class Program
{
    static Type _type = typeof(char); // Store Type as field.

    static void Main()
    {
        Console.WriteLine(_type); // Value type pointer
        Console.WriteLine(typeof(int)); // Value type
        Console.WriteLine(typeof(byte)); // Value type
        Console.WriteLine(typeof(Stream)); // Class type
        Console.WriteLine(typeof(TextWriter)); // Class type
        Console.WriteLine(typeof(Array)); // Class type
        Console.WriteLine(typeof(int[])); // Array reference type
    }
}
System.Char
System.Int32
System.Byte
System.IO.Stream
System.IO.TextWriter
System.Array
System.Int32[]

Enum example. Some common uses of the typeof operator are the Enum static methods, the DataTable class and similar classes, and the ArrayList conversion methods.

Enum.GetName

Enum.Parse

DataTable

Convert ArrayList, Array

using System;

enum AnimalType
{
    Bird
}

class Program
{
    public static void Main()
    {
        string name = "Bird";
        // Use Enum.Parse with typeof argument.
        var result = Enum.Parse(typeof(AnimalType), name);
        // Test result.
        if ((AnimalType)result == AnimalType.Bird)
        {
            Console.WriteLine("OK");
        }
    }
}
OK

Summary. Typeof is an operator. We assigned the result of typeof expressions to a Type field or variable. There are many common uses of the typeof operator in .NET.