Question

• I read a set of data from database first
• Insert a new record using same data in same table.

I tried this but:-

using (var db = new
    DataContext(ConfigurationManager.ConnectionStrings["DB"].ToString()))
{
    var items = from t in db.Table1
                where t.ID.Equals(100)
                select t;
    foreach (var item in items)
    {
        using (var db1 = new
            DataContext(ConfigurationManager.ConnectionStrings["DB"].ToString()))
        {
            Table1 tab = new Table1
            {
                FName = item.FName,
                LName = item.LName,
                Number = item.Number,
            };
            db1.Table1.InsertAllOnSubmit(tab);
            db1.SubmitChanges();
        }
    }
}

I can’t compile it. It throws this error at line ‘db1.Table1.InsertAllOnSubmit(tab)‘:-

‘System.Data.Linq.Table.InsertAllOnSubmit(System.Collections.Generic.IEnumerable)’
cannot be inferred from the usage. Try specifying the type arguments
explicitly.

Answer 1

Your code has some flaws.

You seem to read one Table1 (assuming the id is unique) but you are treating it like a collection

Quick try since you anyway add only one table1 at a time: Replace

db1.Table1.InsertAllOnSubmit(tab); 

by

db1.Table1.InsertOnSubmit(tab); 

If your ID is not unique try:

List<Table1> items = (from t in db.Table1 
            where t.ID.Equals(100) 
            select t).ToList();

The rest of the code can stay the same (but still replace the InsertAllOnSubmit)

Update

You can simplify bigtime:

using (var db = new 
DataContext(ConfigurationManager.ConnectionStrings["DB"].ToString())) 
 { 
Table1 thisTable = (from t in db.Table1 
            where t.ID. == 100
            select t).SingleOrDefault(); 

if ( thisTable != null)
{
        Table1 tab = new Table1 ()
        { 
            FName = item.FName, 
            LName = item.LName, 
            Number = item.Number,                }; 
            db.Table1.InsertOnsubmit(tab)
            db.SubmitChanges(); 
         }
 } 
}

if you are 100% sure your id will always match use .Single() instead of .SingleOrDefault(). Single will throw an exception if no result matches. SingleOrDefault returns NULL in this case.