for gridview

To achieve this without a full page reload, you can use ASP.NET's built-in AJAX functionality, specifically the UpdatePanel control. Here's an example of how you can modify your ASPX page to achieve this:


   
       
           
               
                   
                       
                           
                       
                       
                           
                       
                       
                   
                   
                       
                       
                   
               
           
       
   


Code Behind

 

Protected Sub ddl1_SelectedIndexChanged(sender As Object, e As EventArgs)
    ' Bind ddl2 based on ddl1 selection
    Dim ddl1 As DropDownList = DirectCast(sender, DropDownList)
    Dim ddl2 As DropDownList = DirectCast(ddl1.NamingContainer.FindControl("ddl2"), DropDownList)
    ' Bind ddl2 items
    ddl2.DataSource = ' your data source
    ddl2.DataBind()
End Sub

Protected Sub ddl2_SelectedIndexChanged(sender As Object, e As EventArgs)
    ' Fill txtBox based on ddl2 selection
    Dim ddl2 As DropDownList = DirectCast(sender, DropDownList)
    Dim txtBox As TextBox = DirectCast(ddl2.NamingContainer.FindControl("txtBox"), TextBox)
    ' Fill txtBox with value
    txtBox.Text = ' your value
End Sub

 

By using the UpdatePanel control, you can update the contents of the panel without causing a full page reload. The Triggers section specifies which controls will trigger an asynchronous postback.

In the code-behind, you can access the controls within the UpdatePanel using the NamingContainer property.

Make sure to add the ScriptManager control to your Master Page, and set EnablePartialRendering to true.

This should achieve the desired behavior without a full page reload.