title: How to show hidden dropdown box after a selection is made in another dropdown box in asp.net?
body: <p>I have been having a lot of problems getting this to work, so I have 2 drop downs that I have on my page, and another that I want to hide at first. After a selection is made in the second dropdown (any selection), I want the third dropdown and its Label to become visible. They are all connected to a database. I have recreated that aspect of the code in a simple way to give a visual.
   I have searched the web for help. I am new to .NET and haven't ever used jquery or ajax, if it is possible i would like it in just C#. if you suggest jquery please explain in more detail. The CS page is pretty much empty at this point. Any help is appreciated.</p>
  
  <pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  
  &lt;html xmlns="http://www.w3.org/1999/xhtml" &gt;
  &lt;head id="Head1" runat="server"&gt;
      &lt;title&gt;Dropdowns&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form id="form1" runat="server"&gt;
      &lt;div&gt;
  
  
  
          &lt;asp:DropDownList ID="ddlManu" runat="server" AutoPostBack="True" 
              DataSourceID="SqlDataSource1" DataTextField="Field1" DataValueField="ID" &gt;
          &lt;/asp:DropDownList&gt;    
          &lt;asp:SqlDataSource ID="SqlDataSource1" runat="server" 
              ConnectionString="&lt;%$ ConnectionStrings:ConnectionString %&gt;" 
              ProviderName="&lt;%$ ConnectionStrings:ConnectionString.ProviderName %&gt;" 
              SelectCommand="SELECT [Version] FROM [ProductVersion]"
              DataSourceMode="DataReader"&gt;
              &lt;/asp:SqlDataSource&gt;
  
  
          &lt;asp:DropDownList ID="ddlProduct" runat="server" 
              DataSourceID="SqlDataSource2" DataTextField="Field1" DataValueField="ID" 
              AutoPostBack="True"  &gt;
          &lt;/asp:DropDownList&gt;
  
          &lt;asp:SqlDataSource ID="SqlDataSource2" runat="server" 
              ConnectionString="&lt;%$ ConnectionStrings:ConnectionString2 %&gt;" 
              ProviderName="&lt;%$ ConnectionStrings:ConnectionString2.ProviderName %&gt;" 
              SelectCommand="SELECT [ID], [Field1], [Field2],[FKID] FROM [MSProducts] 
              WHERE FKID = @ID" DataSourceMode="DataReader"&gt;
  
              &lt;SelectParameters&gt;
              &lt;asp:ControlParameter ControlID="ddlManu" Name="ID"
              PropertyName="SelectedValue" DefaultValue="" /&gt;
              &lt;/SelectParameters&gt;
          &lt;/asp:SqlDataSource&gt;
  
          &lt;br /&gt;
          &lt;asp:Label ID="Label1" runat="server" Text="Category1:"&gt;&lt;/asp:Label&gt;
          &lt;asp:DropDownList ID="ddlPop" runat="server" DataSourceID="SqlDataSource1"&gt;
          &lt;/asp:DropDownList&gt;
          &lt;br /&gt;
          &lt;br /&gt;
          &lt;br /&gt;
                      &lt;br /&gt;
                      &lt;br /&gt;
                      &lt;br /&gt; 
  
      &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>