Most of the times, we will have the dropdownlist items in sql server database which needs to be populated when loading the page.

In  this little code snippet, we will try to achieve this by 2 ways,

1. Binding From CodeBehind

ASPX

 <asp:DropDownList ID="ddlRoles" runat="server" Width="10em">

                </asp:DropDownList>

CodeBehind

protected void Page_Load(object sender, EventArgs e)

    {   

        if (!IsPostBack)

        {

         ddlRoles.DataSource = GetAllRoles();

         ddlRoles.DataValueField = "RoleID";

         ddlRoles.DataTextField = "Role";

         ddlRoles.DataBind();

         ddlRoles.Items.Insert(0, new ListItem("Select",""));

        }

    }

public DataTable GetAllRoles()

    {

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Sql"].ConnectionString);

        con.Open();

        SqlCommand com = new SqlCommand("SP_GetAllRoles", con);

        com.CommandType = CommandType.StoredProcedure;

        SqlDataAdapter ada = new SqlDataAdapter(com);

        DataTable dt = new DataTable();

        ada.Fill(dt);

        return dt;

    }

In the above code, I have given the database column name "RoleID" that should be populated for value field of ListItem. Similarly, Role for text field.

2. Binding from ASPX page

We can also bind the dropdownlist from ASPX page by calling function GetAllRoles(). The only constraint is we should make the function as public to access it from ASPX page.

 ASPX

<asp:DropDownList ID="ddlRoles" DataSource='<%# GetAllRoles() %>'

                                DataTextField="Role"  DataValueField="RoleID"

                                SelectedValue='<%# Bind("RoleID") %>' runat="server">

                                </asp:DropDownList>