dropdownlist Insert always the default value - asp.net

Question

I have one dropdownlist with data from database table and i want do insert with this ddl + 2 texbox field in another table . The insert work but always insert the default dropdownList witch displays first. wHat am i missing?
protected void Page_Load(object sender, EventArgs e)
{
string connectionString = cs.getConnection();
string query = "SELECT Id, NAME FROM PROFITCATEGORIES";
using (SqlConnection myConnection = new SqlConnection(connectionString))
{
myConnection.Open();
SqlCommand command = new SqlCommand(query, myConnection);
using (SqlDataReader rdr = command.ExecuteReader())
{
DropDownListCategory.DataSource = rdr;
DropDownListCategory.DataTextField = "Name";
DropDownListCategory.DataValueField = "ID";
DropDownListCategory.DataBind();
}
}
}
protected void ButtonSave_Click(object sender, EventArgs e)
{
if (String.IsNullOrWhiteSpace(TextBoxValue.Text))
return;
string connectionString = cs.getConnection();
string insertSql = "INSERT INTO profits(Value,DateCreate,IdCategory,IdUser) VALUES(#Value, #DateCreate,#CategoryId,#UserId)";
using (SqlConnection myConnection = new SqlConnection(connectionString))
{
myConnection.Open();
SqlCommand command = new SqlCommand(insertSql, myConnection);
//параметризация се прави тук за да се избегне SQL Injection
command.Parameters.AddWithValue("#Value", TextBoxValue.Text);
command.Parameters.AddWithValue("#DateCreate", TextBoxData.Text);
command.Parameters.AddWithValue("#CategoryId", DropDownListCategory.SelectedValue);
command.Parameters.AddWithValue("#UserId", cui.getCurrentId());
command.ExecuteNonQuery();
//пренасочваме заявката към същата страница за да се видят новите резултати и да се избегне проблем с дублиране на инсерт при рефреш на страницата
Response.Redirect("~/Profit.aspx");
myConnection.Close();
}
TextBoxValue.Text = string.Empty;
}

Answer 1

You're re-binding the list on every page load. Wrap the data-binding code in an if (!IsPostBack) block.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// Bind the list here...
}
}

Answer 2

Everytime you press the asp:button the page gets reloaded, and the code in the page_load method gets initialised again. That's why the default item is always inserted in your database.
Put this around your code in the page_load: (if (!Page.IsPostback))
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.isPostback)
{
string connectionString = cs.getConnection();
string query = "SELECT Id, NAME FROM PROFITCATEGORIES";
using (SqlConnection myConnection = new SqlConnection(connectionString))
{
myConnection.Open();
SqlCommand command = new SqlCommand(query, myConnection);
using (SqlDataReader rdr = command.ExecuteReader())
{
DropDownListCategory.DataSource = rdr;
DropDownListCategory.DataTextField = "Name";
DropDownListCategory.DataValueField = "ID";
DropDownListCategory.DataBind();
}
}
}
}

Answer 3

Use the AppendDataBoundItems property and set it to true, and only bind on PostBack:
How Do I Add an Additional Item To a Databound DropDownList Control in ASP.NET?
ListControl.AppendDataBoundItems Property