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Validate ListBox and DropDown List using Required Field Validator

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In Asp.net, sometimes we need to validate ListBox and DropDown List using Required field validator. It is tricky and avoids the use of JavaScript function to validate ListBox and DropDown List. Here I am sharing the code.

Validate DropDown List and ListBox

    

  1.  <form id="form1" runat="server">
    2. 

  2. <div>
    3. 

  3.  <asp:ListBox ID="lstboxCity" runat="server" Width="200px" SelectionMode="Multiple">
    4. 

  4.  <asp:ListItem Value="1">Delhi</asp:ListItem>
    5. 

  5.  <asp:ListItem Value="2">Noida</asp:ListItem>
    6. 

  6.  <asp:ListItem Value="3">Gurgaon</asp:ListItem>
    7. 

  7.  <asp:ListItem Value="4">Mumbai</asp:ListItem>
    8. 

  8.  <asp:ListItem Value="5">Pune</asp:ListItem>
    9. 

  9.  <asp:ListItem Value="6">Banglore</asp:ListItem>
    10. 

  10.  <asp:ListItem Value="7">Lucknow</asp:ListItem>
    11. 

  11.  </asp:ListBox> <asp:RequiredFieldValidator ID="RequiredFieldValidator1" ControlToValidate="lstboxCity" InitialValue="" runat="server" ErrorMessage="Please select atleast one city"></asp:RequiredFieldValidator>
    12. 

  12. </div>
    13. 

  13. <br />
    14. 

  14. <div>
    15. 

  15.  <asp:DropDownList ID="ddlCity" runat="server" Width="200px">
    16. 

  16.  <asp:ListItem Value="0">--Select--</asp:ListItem>
    17. 

  17.  <asp:ListItem Value="1">Delhi</asp:ListItem>
    18. 

  18.  <asp:ListItem Value="2">Noida</asp:ListItem>
    19. 

  19.  <asp:ListItem Value="3">Gurgaon</asp:ListItem>
    20. 

  20.  <asp:ListItem Value="4">Mumbai</asp:ListItem>
    21. 

  21.  <asp:ListItem Value="5">Pune</asp:ListItem>
    22. 

  22.  <asp:ListItem Value="6">Banglore</asp:ListItem>
    23. 

  23.  <asp:ListItem Value="7">Lucknow</asp:ListItem>
    24. 

  24. </asp:DropDownList>
    25. 

  25. <asp:RequiredFieldValidator ID="RequiredFieldValidator2" ControlToValidate="ddlCity" InitialValue="0" runat="server" ErrorMessage="Please select city"></asp:RequiredFieldValidator>
    26. 

  26.  </div>
    27. 

  27.  <br />
    28. 

  28.  <asp:Button ID="btnSubmit" runat="server" Text="Submit" />
    29. 

  29.  </form> 
    30.



Note

For validating DropDown List, make sure you have "--Select--" option value 0 other wise validation on it will not work.
Summary
In this article I try to explain how to validate DropDownList and ListBox using Required Field Validator. I hope after reading this article you will be able to use this trick in your code. I would like to have feedback from my blog readers. Please post your feedback, question, or comments about this article.