Dropdownlist validation in Asp.net Using Required field validator

Question

I have Dropdownlist whose value field and text field are bind at runtime. it has --select-- as first item with a value of 0 and the rest of the values are bind at runtime.

I have given validaton group for both the control and the validator as "g1" and Intialvalue=0

But still the page is posting back even if I select --select-- option.

<asp:DropDownList AutoPostBack="true" CssClass="dropdown" ValidationGroup="g1"      ID="ddlReportType" runat="server"      OnSelectedIndexChanged="ddlReportType_SelectedIndexChanged"></asp:DropDownList>  <asp:RequiredFieldValidator ControlToValidate="ddlReportType" ID="RequiredFieldValidator1" ValidationGroup="g1" CssClass="errormesg" ErrorMessage="Please select a type" InitialValue="0" runat="server"  Display="Dynamic"> </asp:RequiredFieldValidator> 

And code Behind to Bind the Dropdown

ddlReportType.Items.Clear(); ddlReportType.DataSource = dt.Tables[0]; ddlReportType.DataTextField = "ReportType"; ddlReportType.DataValueField = "ReportTypeID"; ddlReportType.DataBind(); ddlReportType.Items.Insert(0, new ListItem("--Select--", "0")); //ddlReportType.Items[0].Value = "0"; ddlReportType.SelectedIndex = 0; 

Answer 1

<asp:RequiredFieldValidator InitialValue="-1" ID="Req_ID" Display="Dynamic"      ValidationGroup="g1" runat="server" ControlToValidate="ControlID"     Text="*" ErrorMessage="ErrorMessage"></asp:RequiredFieldValidator> 

Answer 2

Here use asp:CompareValidator, and compare the value to "select" option.

Use Operator="NotEqual" ValueToCompare="0" to prevent the user from submitting the "select".

<asp:CompareValidator ControlToValidate="ddlReportType" ID="CompareValidator1"     ValidationGroup="g1" CssClass="errormesg" ErrorMessage="Please select a type"     runat="server" Display="Dynamic"      Operator="NotEqual" ValueToCompare="0" Type="Integer" /> 

When you do above, if you select the "select " option from dropdown it will show the ErrorMessage.