Web form using c#

[shapna]

Hi,
I am very new to C#.I am trying to create a webform to save data in SQl server 2008 using c#.My problem is when i click on the save button, the code saves the 1st record every time instead of saving the new record.all my textboxes are showing the 1st record when i am trying to add new record.Below is my code for save button:

Please help me!!!
Shapna

namespace TestWebApp
{
    public partial class About : System.Web.UI.Page
    {
        DataSet ds = new DataSet();
        int MaxRows = 0;
        int inc = 0;
        SqlDataAdapter da;

        protected void Page_Load(object sender, EventArgs e)
        {
            
            string conn = System.Configuration.ConfigurationManager.ConnectionStrings["CnStr"].ConnectionString;
            SqlConnection con = new SqlConnection(conn);
            con.Open();
           
            da = new SqlDataAdapter("Select * from Av_details", con);

            ds.Clear();
            da.Fill(ds, "Av_details");
            NavigateRecords();
            MaxRows = ds.Tables[0].Rows.Count;
            con.Close();
            
        }
           
            private void NavigateRecords()
            {
                DataRow dr;
                dr = ds.Tables[0].Rows[inc];
                TxtInvID.Text = dr.ItemArray.GetValue(0).ToString();
                CBOInvType.SelectedItem.Text = dr.ItemArray.GetValue(1).ToString();
                TxtItemName.Text = dr.ItemArray.GetValue(2).ToString();
                TxtLocation.Text =  dr.ItemArray.GetValue(3).ToString();
                TxtMake.Text = dr.ItemArray.GetValue(4).ToString();
                TxtModel.Text = dr.ItemArray.GetValue(5).ToString();
                TxtSerial.Text = dr.ItemArray.GetValue(6).ToString();
            }

            protected void Cmd_Clear_Click(object sender, EventArgs e)
            {
                TxtInvID.Text = "";
                CBOInvType.SelectedItem.Text = "Select Item Type";
                TxtItemName.Text = "";
                TxtLocation.Text = "";
                TxtMake.Text = "";
                TxtModel.Text = "";
                TxtSerial.Text = "";
            }

           
           
            protected void Cmd_Add_Click(object sender, EventArgs e)
            {
                int maxID;
                maxID = 0;
                maxID = (int)ds.Tables["AV_Details"].Compute("Max(InventoryID)", "")+1;
                
                TxtInvID.Text = maxID.ToString();
                CBOInvType.SelectedItem.Text = "Select Item Type";
                TxtItemName.Text = "";
                TxtLocation.Text = "";
                TxtMake.Text = "";
                TxtModel.Text = "";
                TxtSerial.Text = "";

            }

            protected void Cmd_Save_Click(object sender, EventArgs e)
            {
                System.Data.SqlClient.SqlCommandBuilder cb;
                cb = new System.Data.SqlClient.SqlCommandBuilder(da);                
                
                    DataRow dr = ds.Tables[0].NewRow();
                    string ItemName = TxtItemName.Text.ToString();
                    
                    dr[0] = TxtInvID.Text;
                    dr[1] = CBOInvType.SelectedItem.Text.ToString();
                    dr[2] = TxtItemName.Text.ToString();
                    dr[3] = TxtLocation.Text.ToString();
                    dr[4] = TxtMake.Text.ToString();
                    dr[5] = TxtModel.Text.ToString();
                    dr[6] = TxtSerial.Text.ToString();
                    dr[7] = "A";
                   
                    ds.Tables[0].Rows.Add(dr);
               
                MaxRows = MaxRows + 1;
                inc = MaxRows - 1;

                da.Update(ds, "AV_Details");
                WebMsgBox.Show("Data Added Successfully!!");              
                

            }         
             
            }