Thanks for fast response Angel,

We are using infragistics 10.2 version . I have tried with first two options but i could not see any improvement . So I tried with the third option then there is good improvement. But the problem is when i scroll down the new Items are not loading into drop down . Can you please suggestion me how can i fix this issue.

Following is the code i am using . Visual studio is 2008, infragistics version 10.2.

aspx page in form tag

<form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <div>
     <ig:WebDropDown  ID="WddEmployeeMSC" runat="server" Width="200px" DisplayMode="DropDownList" TextField="Name" ValueField="Id"
     EnableMultipleSelection="false" EnableViewState="false"  EnableLoadOnDemand="true" LoadingItemsMessageText="Loading"   EnableAutoFiltering="Server"  >   
    
    </ig:WebDropDown>
    <asp:Button ID="btnSubmit" Text="Submit" runat="server" OnClick="btnSubmit_Click" />
    <asp:Button ID="btnPopulate" Text="PopulateData" runat="server" OnClick="btnPopulate_Click" />
    </div>
    </form>

Following is the code behind and a class to create and bind generic list to webdropdown.

 protected void btnSubmit_Click(object sender, EventArgs e)
        {
            var text = WddEmployeeMSC.SelectedValue;
            var value = WddEmployeeMSC.SelectedValue;
        }

        protected void btnPopulate_Click(object sender, EventArgs e)
        {
            List<NameList> NameList = new List<NameList>();
            NameList name;
            for (int i = 1; i < 8500; i++)
            {
                name = new NameList() { Name = "Name" + i, Id = i };
                NameList.Add(name);
            }

            WddEmployeeMSC.DataSource = NameList.ToList();
            WddEmployeeMSC.ValueField = "Id";
            WddEmployeeMSC.TextField = "Name";
            WddEmployeeMSC.DataBind();
            WddEmployeeMSC.Items.Insert(0, new DropDownItem("All", "All"));
        }

Following is the class

 class NameList
    {
     
        public int Id { get; set; }
        
        public string Name { get; set; }
    
    }

Thanks in advance.