Validate dropdown when value is set to empty using asp.net web form

Question

  <asp:DropDownList runat="server" ID="ddl">
    <asp:ListItem Text="-Select-" Value=""></asp:ListItem>
    <asp:ListItem Text="One" Value="1"></asp:ListItem>
    <asp:ListItem Text="Two" Value="2"></asp:ListItem>
    <asp:ListItem Text="Three" Value="3"></asp:ListItem>
  </asp:DropDownList>

<asp:CompareValidator ID="cvddl" runat="server" Text="Error" 
ControlToValidate="ddl" Operator="NotEqual" ValueToCompare = ""
ValidationGroup="CreateRolls"></asp:CompareValidator>

I do want to validate dropdown, if select is selected error should be thrown. Main aim is that the value should be empty.

Is there is any methord to validate like this . Please help me with this

You probably need this, http://stackoverflow.com/questions/2280559/how-to-add-a-requiredfieldvalidator-to-dropdownlist-control — Adil, Feb 07 '14 at 05:57
@VigneshMarteen set the initial value as -select- as you have the initial value as select, and dont forget to use the validation group too..!! You need the validation group in the Submit button too, use same validation group — Amarnath Balasubramanian, Feb 07 '14 at 06:04
you can use my code as it is..! it works fine, i have checked myself..!! — Amarnath Balasubramanian, Feb 07 '14 at 06:12

Amarnath Balasubramanian · Answer 1 · 2014-02-07T06:12:03.883

DropDownList

<asp:DropDownList ID="ddl" runat="server"
                  ValidationGroup="CreateRolls"
                  AppendDataBoundItems="true">
  <asp:ListItem Text="-Select-" Value=""></asp:ListItem>
  <asp:ListItem Text="One" Value="1"></asp:ListItem>
  <asp:ListItem Text="Two" Value="2"></asp:ListItem>
  <asp:ListItem Text="Three" Value="3"></asp:ListItem>
</asp:DropDownList>

RequiredFieldValidator

<asp:RequiredFieldValidator ID="rfvDDL" runat="server"
                            ControlToValidate="ddl" 
                            Display="Dynamic"
                            ErrorMessage="Values is required."
                            InitialValue="-Select-"
                            ForeColor="Red"
                            ValidationGroup="CreateRolls" >
</asp:RequiredFieldValidator>

The Important property to be noted in the code is the following

 ControlToValidate="ddl" 
InitialValue="-Select-"
ValidationGroup="CreateRolls"

score 2 · Accepted Answer · answered Nov 28 '18 at 18:01

Edited answer's Amarnath Balasubramanian (I have not permissions to add comments)

DropDownList

<asp:DropDownList ID="ddl" runat="server"
                  ValidationGroup="CreateRolls"
                  AppendDataBoundItems="true">
  <asp:ListItem Text="-Select-" Value="-1"></asp:ListItem>
  <asp:ListItem Text="One" Value="1"></asp:ListItem>
  <asp:ListItem Text="Two" Value="2"></asp:ListItem>
  <asp:ListItem Text="Three" Value="3"></asp:ListItem>
</asp:DropDownList>

RequiredFieldValidator

<asp:RequiredFieldValidator ID="rfvDDL" runat="server"
                            ControlToValidate="ddl" 
                            Display="Dynamic"
                            ErrorMessage="Values is required."
                            InitialValue="-1"
                            ForeColor="Red"
                            ValidationGroup="CreateRolls" >
</asp:RequiredFieldValidator>

The Important property to be noted in the code is the following

ControlToValidate="ddl" 
InitialValue="-Select-"
ValidationGroup="CreateRolls"

Note that changes are

<asp:ListItem Text="-Select-" Value="-1"></asp:ListItem>
InitialValue="-1"

score 1 · Answer 3 · answered Feb 07 '14 at 06:00

   <asp:DropDownList runat="server" ID="ddRoleType">
<asp:ListItem Text="-Select-" Value="-1"></asp:ListItem>
<asp:ListItem Text="One" Value="1"></asp:ListItem>
<asp:ListItem Text="Two" Value="2"></asp:ListItem>
<asp:ListItem Text="Three" Value="3"></asp:ListItem>
  </asp:DropDownList>



<asp:CompareValidator ID="CompareValidator1" runat="server" Text="Error" 
ControlToValidate="ddRoleType" Operator="NotEqual" ValueToCompare = "-1"
ValidationGroup="CreateRolls"></asp:CompareValidator>

or you can use Required field validator

Validate dropdown when value is set to empty using asp.net web form

3 Answers3

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