Data Not Updated using LINQ + sql 2000

[sonia.sardana]

protected void Page_Load(object sender, EventArgs e)
    {
        DataClassesDataContext dbsonia = new DataClassesDataContext();
              
        student result = dbsonia.students.Single(p => p.roll == 1);
        result.Name = "S";        
        dbsonia.SubmitChanges();
     }

I have the following records in the table student(see in fig 1).
I am trying to update the Name of student whose Roll no =1. But Record is not updated in the database,can somebody help me out.