7.12. Static methods

Static methods in C# are very similar to static methods in Java. You declare a static method using the static keyword. A static method belongs to the class as a whole, rather than to a single instance of the class.

Similiarly, you invoke a static method by prefixing the method name with the class name followed by a dot.

 1: using System;
 2:
 3: class MainClass{
 4:   static void Main(){
 5:     TestClass.DoSomething();
 6:   }
 7: }
 8:
 9: class TestClass{
10:   static public void DoSomething (){
11:     Console.WriteLine("running static method");
12:   }
13: }

Output:

c:expt>test
running static method

Like Java

A static method cannot refer to non-static methods or other non-static members.

Unlike Java

You cannot invoke a static method using a reference to an instance of that class. You need to use the class name to invoke a static method, or access a static member. Java allows you to invoke a static method using a variable referring to an instance of the class, as shown in the example below.

You can do this in Java:

 1: // TestMain.java
 2: public class TestMain{
 3:   public static void main(String args[]){
 4:     TestClass c = new TestClass();
 5:     c.doSomething(); // or TestClass.doSomething();
 6:   }
 7: }
 8: class TestClass{
 9:   public static void doSomething(){
10:     System.out.println("running static method");
11:   }
12: }

However in C#, this will give a compilation error:

 1: using System;
 2: public class TestMain{
 3:   public static void Main(){
 4:     TestClass c = new TestClass();
 5:     c.DoSomething(); // use TestClass.DoSomething();
 6:   }
 7: }
 8: class TestClass{
 9:   public static void DoSomething(){
10:     Console.WriteLine("running static method");
11:   }
12: }

Compilation error:

Test.cs(4,5): error CS0176: Static member
'TestClass.DoSomething()' cannot be accessed with an
instance reference; qualify it with a type name instead

Additional notes

• The static keyword can be used with fields, methods, properties, operators, and constructors, but cannot be used with indexers, destructors, or types.

• Static function members (methods, instance constructors, properties, and operators) are always non-virtual.

• A static member cannot be declared with the following modifiers: virtual, override, and abstract.