title: 'System.Data.Entity.Infrastructure.DbUpdateException' occurred in EntityFramework.dll
body: <p>I wrote a rather simple code (client server based on WCF and Windows form).
  i was trying to update the db so that i could test my code and i encounterd the above exception.
  Any ideas how to solve it?</p>
  
  <pre><code>      // For testing 
        public void updateTable() 
        {
          using (var db = new overlayDBEntities())
          {
              var overlaydb = new overlayData
              {
                  DeviceId = "1111",
                  TimestampUTC = new DateTime(1990, 1, 1, 9, 9, 9),
                  OverlayData1 = "Random Text"
              };
  
              db.overlayData.Add(overlaydb);
  
              try
              {
                  db.SaveChanges();
              }
              catch(Exception ex)
              {
                  Console.WriteLine(ex.Message);
              }
              var overlaydb1 = new overlayData
              {
                  DeviceId = "1111",
                  TimestampUTC = new DateTime(2000, 2, 2, 10, 10, 10),
                  OverlayData1 = "seconed seconed seconed "
              };
  
              db.overlayData.Add(overlaydb);
  
              try
              {
                  db.SaveChanges();
              }
              catch (Exception ec) 
              {
                  Console.WriteLine(ec.Message);
              }
          }
      }
  </code></pre>