Understanding Static Constructors in C#

Understanding Static Constructors in C#

In C#, a static constructor is a special constructor used to initialize static members of a class or perform actions that need to happen only once, for the entire type rather than per instance.

 

What Is a Static Constructor?

A static constructor is declared using the static keyword and is called automatically by the .NET runtime before the first instance is created or any static members are accessed.

Syntax:

static ClassName()

{

    // Initialization code here

}

 

Key Characteristics

• Declared with static keyword
• No parameters are allowed
• No access modifiers (it is always private implicitly)
• Executed automatically, once per type
• Cannot be called directly
• Useful for initializing static fields or performing one-time setup

 

Code Example

using System;

 

public class MyClass

{

    public static int StaticValue;

 

    // Static Constructor

    static MyClass()

    {

        Console.WriteLine("Static constructor called");

        StaticValue = 100;

    }

 

    // Instance Constructor

    public MyClass()

    {

        Console.WriteLine("Instance constructor called");

    }

}

 

class Program

{

    static void Main()

    {

        Console.WriteLine(MyClass.StaticValue); // Triggers static constructor

        MyClass obj = new MyClass();            // Then calls instance constructor

    }

}

 

Output

Static constructor called

100

Instance constructor called

 

Use Cases

• Initializing static fields
• Setting up configuration or environment data at the class level
• Ensuring one-time setup before class usage
• Connecting to external resources or caching mechanisms

 

Difference: Static vs Instance Constructor

Feature	Static Constructor	Instance Constructor
Invocation Time	First time class is used	Each time an object is created
Parameters	Not allowed	Allowed
Access Modifiers	Not allowed (always private)	Allowed
Manual Invocation	Not possible	Can be called with new

 

Summary

Static constructors in C# are powerful tools for ensuring that static data and logic are initialized once, automatically, and in a thread-safe manner. They are especially valuable when there is a need to prepare a class for use before any members—static or instance—are accessed.