title: Linq db.submitchanges() not working
body: <p>I am facing issue in submit changes in table using linq code executed successfully by it is not saving changes in table.</p>
  
  <p>Some one says your table must have primary key to submit changes but my table have primary key.</p>
  
  <p>Some one says use integrated security = true to but it generate exception invalid keyword integrated security </p>
  
  <p>Here is my connection string</p>
  
  <pre><code>&lt;add name="POSConnectionString" connectionString="Persist Security Info=False; Data Source=|DataDirectory|\App_Data\POS.sdf; mode=Read Write;"
      providerName="Microsoft.SqlServerCe.Client.4.0" /&gt; 
  </code></pre>
  
  <p>Code to insert data in table</p>
  
  <pre><code>public bool InsertItem(Item item)
  {
      try
      {
          using (SqlCeConnection conn = new SqlCeConnection(connectionString))
          {
              using (POSContext db = new POSContext(conn))
              {                        
                  db.Items.InsertOnSubmit(item);
                  db.SubmitChanges();
                  return true;
              }
          }
      }
      catch (Exception ex)
      {
          return false;
      }
  
  }
  </code></pre>
  
  <p>Here is my table script</p>
  
  <pre><code>CREATE TABLE [Item] (
    [ItemID] int IDENTITY (1,1) NOT NULL
  , [ItemName] nvarchar(100) NOT NULL
  , [ItemCode] nvarchar(100) NOT NULL
  , [Weight] int NOT NULL
  , [IsActive] bit NOT NULL
  , [Stock] int NULL
  , [UnitID] int NULL
  );
  GO
  ALTER TABLE [Item] ADD CONSTRAINT [PK_Item] PRIMARY KEY ([ItemID]);
  GO
  </code></pre>
  
  <p>I am working in windows form application development 
  Database Sql server compact database 4.0
  Visual studio 2012</p>