server side validation in asp.net application not working

Question

I am putting server side validation but seems it's not working in the way it should. Below is sample code

     //Validation

    private void validation()
    {
        if (txtFName.Text == string.Empty) { Alert("Invalid Name"); return; }

        if (txtLName.Text == string.Empty) { Alert("Invalid Name"); return; }
    }


       // Alert mesage
  public void Alert(string msg)
    {
        ClientScript.RegisterStartupScript(typeof(Page), "SymbolError", "<script
         type='text/javascript'>alert('" + msg + "');</script>");
    }

In my button next click event I am calling this function like

    protected void button_Click(object sender, EventArgs e)
    {
        validation();
    }

Surprisingly, even though I don't enter anything in the texbox (means textbox is empty) ... no alert is coming. Whereas, it should alert.

Can someone point me what I am doing wrong. Appreciate your help.

EDIT:

Most weired thing is that, the same code work fine in other page(s). it alerts fine if the fields are empty or validation failing. Not sure what wrong with this page.

Fe pointer like ... This particular aspx page ... has lot of user controls and those controls ascx page have Javascript. I that could be any issue

Answer 1

I just tried following code.

protected void Button1_Click(object sender, EventArgs e)
{
    validation();
}

private void validation() 
{ 
    Alert("Invalid Name"); 
} 


   // Alert mesage 
public void Alert(string msg) 
{ 
    ClientScript.RegisterStartupScript(typeof(Page), "SymbolError", "<script type='text/javascript'>alert('" + msg + "');</script>"); 
} 

seem like everything is working fine. check out this see if there is any settings issue. (not sure i m just doing trial and error).

http://bytes.com/topic/asp-net/answers/518330-clientscript-registerstartupscript