Validate empty (blank) value on ASP.Net TextBox using C# and VB.Net

Hi Santosh83,

Please refer below sample.

HTML

<table>
    <tr>
        <td>Name:<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="rfvName" runat="server" ErrorMessage="Name is required!"
                ControlToValidate="txtName" Display="Dynamic" ForeColor="Red" ValidationGroup="g1"></asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td>Country:<asp:TextBox ID="txtCountry" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="rfvCountry" runat="server" ErrorMessage="Country is required!"
                ControlToValidate="txtCountry" Display="Dynamic" ForeColor="Red" ValidationGroup="g1"></asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td>
            <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="Submit" ValidationGroup="g1" /></td>
    </tr>
</table>

Code

C#

protected void Submit(object sender, EventArgs e)
{
    txtName.Text = string.Empty;
    txtCountry.Text = string.Empty;
}

VB.Net

Protected Sub Submit(ByVal sender As Object, ByVal e As EventArgs)
    txtName.Text = String.Empty
    txtCountry.Text = String.Empty
End Sub

Screenshort