ASP.NET DropdownList Always insert the first item - asp.net

Question

I have dropdownlist on my website. When I select the any item to insert the database but it does not insert selected item always insert the first item inside the dropdown list. Please Help How can I solve that problem?
Here is my code:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GetCategory();
}
}
void GetCategory()
{
dlCategory.DataSource = Data.GetDataTable("SELECT * FROM tblCategory");
dlCategory.DataTextField = "CategoryName";
dlCategory.DataValueField = "ID";
dlCategory.DataBind();
dlCategory.Items.Insert(0, new ListItem("--Select--", "0"));
dlCategory.SelectedIndex = dlCategory.Items.IndexOf(dlCategory.Items.FindByText("--Select--"));
}
SqlConnection baglanti = Data.baglan();
SqlCommand tr = new SqlCommand("Insert tblProduct (CategoryID) values(#CategoryID)", baglanti);
tr.Parameters.AddWithValue("#CategoryID", dlCategory.SelectedValue);
tr.ExecuteNonQuery();

Answer 1

Your question is a bit blurry regarding the code, so correct me if I misunderstood, but I presume you want to do the following in WebForms:
Simply show all available categories that can be assigned to a
product
When the user selects the category and hits submit, it will be inserted to the DB assegnied to it
It is not quite elegant, but I would put something like this:
private SqlConnection _sqlConnection = new SqlConnection();
protected void Page_Load(object sender, EventArgs e)
{
_sqlConnection.ConnectionString = #".." //Assign whatever your ConnectionString is in Data.baglan();
_sqlConnection.Open();
if (!IsPostBack)
{
GetCategory();
}
else
{
//Define your insert something like this, and I would put this into the submit Button_Click event:
if (!String.IsNullOrEmpty(dlCategory.SelectedValue) && dlCategory.SelectedValue != "0")
{
SqlCommand tr = new SqlCommand("Insert tblProduct (CategoryID) values (#CategoryID)", _sqlConnection);
tr.Parameters.AddWithValue("#CategoryID", dlCategory.SelectedValue);
tr.ExecuteNonQuery();
}
else
{
//TODO: Handle wrong selection, eg display an error message..
}
}
}
void GetCategory()
{
dlCategory.DataSource = new SqlCommand("SELECT * FROM tblCategory", _sqlConnection).ExecuteReader();
dlCategory.DataTextField = "CategoryName";
dlCategory.DataValueField = "ID";
dlCategory.DataBind();
dlCategory.Items.Insert(0, new ListItem("--Select--", "0"));
dlCategory.SelectedIndex = dlCategory.Items.IndexOf(dlCategory.Items.FindByText("--Select--"));
}