ASP.Net Update Panel Dropdownlist Abnormal Behaviour

ASP.Net Update Panel Dropdownlist Abnormal Behaviour: while selecting value some other item gets selected or lost its state in asyncpostback. To resolve the issue check that  DataValueField is having unique values


asp:UpdatePanel ID="UpdatePanel2" runat="server">Triggers>
                   asp:AsyncPostBackTrigger ControlID="ddlMoU" EventName="SelectedIndexChanged"



asp:DropDownList ID="ddlMoU" runat="server" datatextfield="mou" DataValueField="mou" AutoPostBack="True" OnSelectedIndexChanged="ddlMoU_SelectedIndexChanged" EnableViewState="true"