ผมจะเก็บวันที่ลงดาต้าเบสแล้วมันขึ้นว่า Conversion failed when converting date and/or time from character string.

 protected void bt_Save_Click(object sender, EventArgs e)
        {
              
                  string user = txt_UserName.Text ,pass=txt_PassWord.Text, name = txt_Name.Text , lastname=txt_SurName.Text, phone= txt_Phone.Text,mail=txt_EMail.Text, brith=""+ddb_BirthDay.Text+""+ddb_BirthMonth.Text+""+ddb_BirthYear.Text ;
                  string HomeNum = txt_HomeNum.Text, Tambol = txt_tambol.Text, Amphor = txt_Auphor.Text, Province = txt_Province.Text, PostCode = txt_ZipCode.Text;
                  
                  string strConn = WebConfigurationManager.ConnectionStrings["ezyPetShopConnectionString"].ConnectionString;
                  SqlConnection Conn = new SqlConnection(strConn);
                  Conn.Open();
                  string sqlregist1 = "INSERT INTO Customer(Username,Password,CustomerName,CustomerLastName,CustomerPhone,CustomerEMail,CustomerBrith) VALUES (@user,@pass,@name,@lastname,@phone,@mail,@brith) ";
                  string sqlregist2 = "INSERT INTO Customer_Address(Username,HomeNum,Tambol,Amphor,Province,PostCode) VALUES (@user,@HomeNum,@Tambol,@Amphor,@Province,@PostCode) ";
                  SqlCommand com = new SqlCommand(sqlregist1,Conn);
                  com.Parameters.AddWithValue("@user",user);
                  com.Parameters.AddWithValue("@pass", pass);
                  com.Parameters.AddWithValue("@name", name);
                  com.Parameters.AddWithValue("@lastname", lastname);
                  com.Parameters.AddWithValue("@phone", phone);
                  com.Parameters.AddWithValue("@mail", mail);
                  com.Parameters.AddWithValue("@brith", brith);
                  SqlCommand com2 = new SqlCommand(sqlregist2, Conn);
                  com2.Parameters.AddWithValue("@user",user);
                  com2.Parameters.AddWithValue("@HomeNum", HomeNum);
                  com2.Parameters.AddWithValue("@Tambol", Tambol);
                  com2.Parameters.AddWithValue("@Amphor", Amphor);
                  com2.Parameters.AddWithValue("@Province", Province);
                  com2.Parameters.AddWithValue("@PostCode", PostCode);
                  com.ExecuteNonQuery();
                  com2.ExecuteNonQuery();
             
        }