Problen in insert value in database using entity framework in n-tier arch

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ASP.NET

I have 3 column in my table ID,Status,feedback.Id is identity,status value bydefault is false and I have to insert value of feedback using entity framework in n-tier arch.

I made 3 classes as

BO

namespace problemvisa
{
    public class Bo
    {
        private int id;
 
        public int Id
        {
            get { return id; }
            set { id = value; }
        }
        private string status;
 
        public string Status
        {
            get { return status; }
            set { status = value; }
        }
        private string feedback;
 
        public string Feedback
        {
            get { return feedback; }
            set { feedback = value; }
        }
    }
}

2-DAL

public class DAL
{
    public bool insert(Bo aa)
    {
        if (aa.Equals(null))
        {
            return false;
        }
        else
        {
            using (problemEntities1 context = new problemEntities1())
            {
                Table1 tt = new Table1();
                 context.AddToTable1(tt);
                 context.SaveChanges();
            }
            return true;
        }
    }
}

3.BAL

public class BAL
{
    public bool insert(Bo ss)
    {
        DAL dd = new DAL();
        if (dd.insert(ss))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

IN aspx form

protected void Button1_Click(object sender, EventArgs e)
{    
    Bo aa = new Bo();
    aa.Status = "false";
    aa.Feedback = TextBox1.Text;
    BAL ss = new BAL();
    ss.insert(aa);
}

One error is coming i.e.Cannot insert the value NULL into column 'feedback', table 'problem.dbo.Table1'; column does not allow nulls. INSERT fails.
The statement has been terminated.