How do I create any array with a struct which contains an array?

Question

I am very new to C# and I want to create an array of 200 records with each record structured as follows:

struct ChangeRec

{ public datetime TimeStamp;

 public int Last ;

public int [] mode

}

The problem is how do I initialize the mode array to 20 records, and how do I access the array dynamically?   I am not bound to use a struct etc, I just need the functionality of an array that has the mode array as part of its record structure.