在C＃中，是否在调用main（）方法之前初始化所有静态变量？

Question

The ones I am particularly concerned about are:

• static variables in classes that are defined in referenced/dependency classes, contained in external DLLs. In my example, none of the types in that third party assembly is reference until later in the program. (let's say 5 min into execution).

Will the static variables of that third-party assembly only be loaded then?

Thanks, rui

Answer 1

according to C# spec which says:

If a static constructor exists in the class, execution of the static field initializers occurs immediately prior to executing that static constructor. Otherwise, the static field initializers are executed at an implementation-dependent time prior to the first use of a static field of that class. The example

whiteout a static constructor you can not predict exactly when a static variable is initialized but they are guaranteed to be initialized before their first use. but for sure they are not initialized before you reference their assemblies

Answer 2

All static fields are initialized before they are first used. This can be done by a type initializer (static constructor) explicitly declared or implicitly provided by the compiler. Static fields that do not have a value assigned in the class declaration will be initialized to the default value of their corresponding type.

Answer 3

Be careful if your static fields are object references whose constructors may throw exceptions:

class Foo
{
    public Foo() { throw new Exception("boom"); }
}
class Bar
{
    private static Foo baz = new Foo();
    public Bar()
    {
        //trying to create a Bar will throw TypeInitializationException
    }
    public static void BarNone()
    {
        //trying to call a static method on Bar will throw TypeInitializationException
    }
}

You'll get a TypeInitializationException when Bar is first used (either constructed or when a static method on Bar is called), as shown above.