title: Changing property of a value in a list without changing the value itself
body: <p>I have a list with values in it (These are types from a class Class1). Every single value has a Date property in it. Now I'm trying this when one element gets added to the list:</p>
  
  <pre><code> var entry = list.First();
              list.Add(entry);
              list.First().DateVal = new DateTime(list.First().DateVal.Value.Year,1,1); 
  </code></pre>
  
  <p>So I'm copying the element and changing the property DateVal to 01.01.xxxx. What happens is that it also changes the whole value to 01.01.xxxx. This happens for both values. Example:</p>
  
  <p>value: 05.10. property: 05.10.2015</p>
  
  <p>After that I get:</p>
  
  <p>value: 01.01. property: 01.01.2015
  value: 01.01. property: 01.01.2015</p>
  
  <p>What I want is:</p>
  
  <p>value: 05.10. property: 01.01.2015
  value: 05.10. property: 05.10.2015</p>
  
  <p>How to just Change the property? I'm wondering why the Code above does not work.</p>