In this article I will explain with an example, how to show and hide TextBox based on DropDownList selection in ASP.Net using C# and VB.Net.
When the YES item (option) is selected in the DropDownList, TextBox will be visible else the TextBox will be hidden in ASP.Net using C# and VB.Net.
 
 

HTML Markup

The HTML Markup consists of:

DropDownList

DropDownList has been assigned with OnSelectedIndexChanged event handler and AutoPostBack property.
Panel – It is hidden by setting Visible property to False.
TextBox – For capturing Passport Number.
Do you have Passport?
<asp:DropDownList ID="ddlHasPassport" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DropDownList_Changed">
    <asp:ListItem Text="No" Value="N" />
    <asp:ListItem Text="Yes" Value="Y" />
</asp:DropDownList>
<hr />
<asp:Panel ID="pnlTextBox" runat="server" Visible="false">
    Passport Number:
<asp:TextBox ID="txtPassport" runat="server" />
</asp:Panel>
 
 

Showing Hiding TextBox based on DropDownList selection in ASP.Net

When an item (option) is selected in the DropDownList, the selected value is checked.
If the selected value is Y (Yes), then the TextBox will be visible else the TextBox will be hidden.
C#
protected void DropDownList_Changed(object sender, EventArgs e)
{
    if (ddlHasPassport.SelectedItem.Value == "Y")
    {
        pnlTextBox.Visible = true;
    }
    else
    {
        pnlTextBox.Visible = false;
    }
}
 
VB.Net
Protected Sub DropDownList_Changed(ByVal sender As Object, ByVal e As EventArgs)
    If ddlHasPassport.SelectedItem.Value = "Y" Then
        pnlTextBox.Visible = True
    Else
        pnlTextBox.Visible = False
    End If
End Sub
 
 

Screenshot

Show Hide TextBox based on DropDownList selection in ASP.Net
 
 

Demo

View Demo
 
 

Downloads

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