我想在ASP.NET中的页面加载时绑定来自SQL Server表列的数据，但是它不起作用

Question

I want to bind data from a SQL Server table column at page load in ASP.NET, but it is not working; code is working in a button click.

This is my code - can anyone help please?

if (!IsPostBack)
{
    DataTable subjects = new DataTable();

    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["con"].ToString());
    SqlDataAdapter adapter = new SqlDataAdapter("SELECT [name] FROM [supplier]", con);
    adapter.Fill(subjects);

    con.Open();

    DropDownreturn.DataSource = subjects;
    DropDownreturn.DataTextField = "name";
    DropDownreturn.DataValueField = "name";
    DropDownreturn.DataBind();
    DropDownreturn.Items.Insert(0, new ListItem("Select", "NA"));

    con.Close();
}

Answer 1

but it is not working; code is working in a button click.

When user press a button then it create a postback if Postback is enabled on button and you have placed !IsPostBack check that may be preventing the code block to bind the dropdown.

To solve this issue.. At Page_Load, check if your button raised the postback then execute the code to bind the dropdown by following below suggested approach:

Which control caused the postback?

Way To Know Which Control Has Raised PostBack

if(IsPostBack)
{
  if(postbackcontrol is button1)
  {
     //Bind dropdown 
  }
}