Void

In C# void means that a method returns no value. Void is useful in many programs. But there are some compile-time errors that may be involved.

Void methods receive parameters like all methods. They use a simple "return" statement that is followed by a semicolon.

First example

The void keyword is common and useful. It indicates the evaluation stack of a method must be empty when it returns. And no value will be copied into the calling code.

Here We declare and use a static void method (Example1). The control flow jumps to this method when you invoke it, but there is no result.

Note It is a compile-time error to assign to the Example method invocation. No variable can be assigned to void.

Next We use an instance void method. To declare an instance method, omit the static modifier. Methods are by default considered instance.

using System;

class Program
{
    static void Example1()
    {
        Console.WriteLine("Static void method");
    }
    void Example2()
    {
        Console.WriteLine("Instance void method");
        return; // Optional
    }

    static void Main()
    {
        //
        // Invoke a static void method.
        //
        Example1();
        //
        // Invoke an instance void method.
        //
        Program program = new Program();
        program.Example2();
        //
        // This statement doesn't compile.
        //
        // int x = Example1();
    }
}Static void method
Instance void method

IL

We look at the intermediate language generated by the Microsoft C# compiler for the first example method. The intermediate language (IL) relies on an evaluation stack for processing.

Detail The void method must have no elements on the evaluation stack when the "ret" instruction is reached.

.method private hidebysig static void Example1() cil managed
{
    .maxstack 8
    L_0000: ldstr "Static void method"
    L_0005: call void [mscorlib]System.Console::WriteLine(string)
    L_000a: ret
}

Error, notes

An error occurs when you try to assign a variable to the result of a void method. This is the "cannot implicitly convert type" error. To fix this, do not assign to void.

Info Because void primarily impacts the compile-time processing of a program, no errors will be caused by void specifically at runtime.

Detail The void type will instead force compile-time errors. These are useful—they help us improve programs.

class Program
{
    static void VoidMethod()
    {
    }

    static void Main()
    {
        int result = VoidMethod();
    }
}Error 1:
Cannot implicitly convert type void to int.

Overload, error

A compile-time error can be raised when you try to overload methods based on only their return types. This cannot be done.

Important You cannot overload methods based on their return types such as void alone in the C# language.

The void keyword can be used on instance and static methods in the C# language. It is common in C# source code. It means that the code returns no value.