When should I use a static constructor?

• A static constructor is used to initialize any static data, or to perform a particular action that needs to be performed once only. It is called automatically before the first instance is created or any static members are referenced.
• A static constructor does not take access modifiers or have parameters.
• A static constructor is called automatically to initialize the class before the first instance is created or any static members are referenced.
• A static constructor cannot be called directly.
• The user has no control on when the static constructor is executed in the program.
• A typical use of static constructors is when the class is using a log file and the constructor is used to write entries to this file.
• Static constructors are also useful when creating wrapper classes for unmanaged code, when the constructor can call the LoadLibrary method.
• If a static constructor throws an exception, the runtime will not invoke it a second time, and the type will remain uninitialized for the lifetime of the application domain in which your program is running.

class SimpleClass
{
    
    // Static variable that must be initialized at run time.
    static readonly long baseline;
       
    // Static constructor is called at most one time, before any
    // instance constructor is invoked or member is accessed. 
    static SimpleClass()
    {
        baseline = DateTime.Now.Ticks;
    }
}

MSDN >> Static constructors

MSDN >> C# Language specification >> Static constructors