title: how to keep old data record while updating asp .net mvc 5
body: <p>I am creating a financial application using with <code>Asp .net mvc5 with EF6</code>.I have a big puzzle about updating database. What I want is that I have <code>Person</code> table <code>(e.g. firstname, lastname, address, salary, tax, and so on)</code>. For the first time, I entered a record <code>(e.g. John, Smith, US, 3500.00,)</code>. When <code>John Smith</code> gets promotion, I will update his salary as <code>4000.00</code> while I am still wanting to keep his old salary <code>3500.00</code>. If I don't keep his <code>3500.00</code>, his <code>tax</code> and <code>other deductible</code> fees from his <code>3500.00</code> salary won't <code>reflect correctly</code> upto the last day that he earned <code>3500.00</code>. Data of his tax all along getting <code>3500.00</code> will lose and will reflect based on <code>4000.00</code>.</p>
  
  <p>Can anyone guide me on how to solve this, please? Appreciate if you can share any resources or links that I can study for this kind of problem. Thank in advance.</p>