How to add another item in linq?

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LINQ

Hi,
I'm using linq to sql. In my program at the beginning, a list is loaded from the SQL database. Then user can add another items. Items are not saved immediately therefore I can not use InsertOnSubmit method in my DB table. I have to save item in the main linq variable and when the user pushes SAVE button it has to be saved.
I tried many ways to add an item in linq variable but none of them worked.

Can anyone help me?

static public void add(UserLoginData item)
{
    try
    {
        item.Order = GetNewOrder();
        UserLoginData[] item_array=new UserLoginData[]{item};
        var usersA = from c in users
                     orderby c.Order
                     select c;
        var usersB = from c in item_array
                     select c;
        var usersC=    usersA.Union(usersB);//related to this error: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
        MainListUsers = from c in usersA
                orderby c.Order
                select c;
        ListRefresh();
    }
    catch (Exception ex)
    {
        Logging.Log.Report(ex.Message, "Error", new System.Diagnostics.StackFrame(true));
    }

}

Christian Graus wrote:

It's a SQL database. Why do you need to use LINQ ?

Therefore what is Linq-to-SQL for?