C# - typeof Operator - Dot Net Perls

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.

Info The typeof operator uses reflection to access the metadata descriptions of the types.

Here We display the string representation of these Type pointers. We assign the result of the typeof operator to a Type variable or field.

Console.WriteLine

Tip This program calls ToString on the Type pointers—this returns a string representation of the type.

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

Here We use Enum.Parse with a typeof argument. With typeof, we get a Type and we use this as the first argument.

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"); } } }

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.

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This page was last updated on Sep 12, 2024 (new example).

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