Implementing a template method template in C #

The template method template provides that the abstract base class does not have an overridable method: this method implements a general algorithm and should not be redefined in subclasses. In Java, a template method is declared finalin an abstract base class, in C # the keyword sealedhas a similar meaning, but no overridden method can not be declared sealed.

public abstract class Base
{
    protected abstract AlgorithmStep1();

    protected abstract AlgorithmStep2();

    public sealed void TemplateMethod()   // sealed: compile error
    {
        AlgorithmStep1();
        AlgorithmStep2();
    }
}

How can I solve this problem? Why can't you forbid a method to redefine subclasses (in C #)?