In this article I will explain with an example, how to disable an item (option) i.e. make not Selectable in ASP.Net DropDownList using C# and VB.Net.
 
 
Database
I have made use of the following table Customers with the schema as follows.
Make First (Default) item (option) not Selectable in ASP.Net DropDownList using C# and VB.Net
I have already inserted few records in the table.
Make First (Default) item (option) not Selectable in ASP.Net DropDownList using C# and VB.Net
 
Note: You can download the database table SQL by clicking the download link below.
          Download SQL file
 
 
HTML Markup
The HTML Markup consists of an ASP.Net DropDownList which will be populated from database.
<asp:DropDownList ID = "ddlCustomers" runat="server">
</asp:DropDownList>
 
 
Namespaces
You will need to import the following namespaces.
C#
using System.Data;
using System.Configuration;
using System.Data.SqlClient;
 
VB.Net
Imports System.Data
Imports System.Configuration
Imports System.Data.SqlClient
 
 
Disable DropDownList Item (Option) in ASP.Net
Inside the Page Load event of the page, the DropDownList is populated with the records of the Customers Table using SqlDataReader. For more details about populating DropDownList using SqlDataReader, please refer my article Bind (Populate) ASP.Net DropDownList using DataReader in C# and VB.Net.
Once the records from database are populated, a default item (option) is inserted at the first position and is marked as Selected. Finally the default item (option) is disabled (not selectable) by adding HTML disabled attribute.
C#
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT CustomerId, Name FROM Customers"))
            {
                cmd.CommandType = CommandType.Text;
                cmd.Connection = con;
                con.Open();
                ddlCustomers.DataSource = cmd.ExecuteReader();
                ddlCustomers.DataTextField = "Name";
                ddlCustomers.DataValueField = "CustomerId";
                ddlCustomers.DataBind();
                con.Close();
            }
        }
 
        //Add a default item at first position.
        ddlCustomers.Items.Insert(0, new ListItem("Please select", ""));
 
        //Set the default item as selected.
        ddlCustomers.Items[0].Selected = true;
 
        //Disable the default item.
        ddlCustomers.Items[0].Attributes["disabled"] = "disabled";
    }
}
 
VB.Net
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As New SqlConnection(constr)
            Using cmd As New SqlCommand("SELECT CustomerId, Name FROM Customers")
                cmd.CommandType = CommandType.Text
                cmd.Connection = con
                con.Open()
                ddlCustomers.DataSource = cmd.ExecuteReader()
                ddlCustomers.DataTextField = "Name"
                ddlCustomers.DataValueField = "CustomerId"
                ddlCustomers.DataBind()
                con.Close()
            End Using
        End Using
 
        'Add a default item at first position.
        ddlCustomers.Items.Insert(0, New ListItem("Please select", ""))
 
        'Set the default item as selected.
        ddlCustomers.Items(0).Selected = True
 
        'Disable the default item.
        ddlCustomers.Items(0).Attributes("disabled") = "disabled"
    End If
End Sub
 
 
Screenshot
Disable DropDownList Item (Option) in ASP.Net using C# and VB.Net
 
 
Demo
View Demo
 
 
Downloads
Download Code