<label>Account Name</label>
   <asp:DropDownList ID="ddlAccName" runat="server" required="required" AutoPostBack="true" OnSelectedIndexChanged="ddlAccName_SelectedIndexChanged" Enabled="false"></asp:DropDownList>

protected void ddlAccName_SelectedIndexChanged(object sender, EventArgs e)
{
    string accname = ddlAccName.SelectedItem.ToString();
    accname = accname.Replace("Saving", "").Replace("Loan", "");
    txtHeading.Text = accname.ToString();

    int check = isNominee(3, ddlAccName.SelectedItem.ToString());
    if (check == 1)
    {
        txtDeposit.Enabled = true;
        txtWithdraw.Enabled = true;
        txtSavingBalance.Enabled = true;


    }
    if (check == 0)
    {
        txtDeposit.Enabled = true;
        txtWithdraw.Enabled = true;
        txtSavingBalance.Enabled = false;
    }
}