// Declare a delegate type
public delegate double MyDelegateType(double x);

// Define some consummer that uses functions of the delegate type
public double Consummer(double x, MyDelegateType f){
    return f(x);
}


//...


// Define a function meant to be passed to the consummer 
// The only requirement is that it matches the signature of the delegate
public double MyFunctionMethod(double x){
    // Can add more complicated logic here
    return x;
}
// In practice now
public void Client(){
    double result = Consummer(1.234, x => x * 456.1234);
    double secondResult = Consummer(2.345, MyFunctionMethod);
}