title: C# Entity Framework: Update Query Does not work
body: <p>I have this simple code : (update value)</p>
  
  <p>I'm trying to update column  "c"</p>
  
  <pre><code> using (MaxEntities ctx = new MaxEntities())
              {
                  aa orders = (from order in ctx.aa
                               select order).First();
                  orders.c = 22;
                  ctx.SaveChanges();
              }
  </code></pre>
  
  <p>this is the table : </p>
  
  <pre><code>CREATE TABLE [dbo].[aa](
      [a] [int] NULL,
      [b] [int] NOT NULL,
      [c] [int] NOT NULL
  ) ON [PRIMARY]
  </code></pre>
  
  <p>and values inside : 
  <img src="https://i.stack.imgur.com/ZSJVP.jpg" alt="enter image description here"></p>
  
  <p>but i get an exception : </p>
  
  <p><em>The property 'c' is part of the object's key information and cannot be modified.</em></p>
  
  <p><img src="https://i.stack.imgur.com/quOCy.jpg" alt="enter image description here"></p>
  
  <p>I'm new to EF.</p>
  
  <p>any help will be much appreciated.</p>