C# .NET - how to stop asp.net get blinking if i give dropdownlist postback=true?

in my asp.net web page get blinking after i gave dropdownlist postback=true..how to stop that blinking if i give dropdownlist postback=true(its must for my pag)?????? 

Use UpdatePanel like this-

 <asp:UpdatePanel ID="updBeerCat" runat="server">
        <ContentTemplate>
          <asp:DropDownList ID="DropDownList2" runat="server" OnTextChanged="drp_SelectedIndexChanged"
            OnSelectedIndexChanged="drp_SelectedIndexChanged" AutoPostBack="true">
            <asp:ListItem>1 </asp:ListItem>
            <asp:ListItem>2 </asp:ListItem>
          </asp:DropDownList>

  </ContentTemplate>
      </asp:UpdatePanel>

Your problem appears somewhat same as http://www.eggheadcafe.com/community/asp-net/17/10460532/user-controls-dropdown-causing-full-postback-inside-updatepanel.aspx

So in that case I would recommend you to register the dropdownlist control as asyncpostback control in Page_Load as:

scriptManager.RegisterAsyncPostBackControl(dropdownlistID);

Let us know if it helped or not.