Question

I’m working with a simple asp.net barcode application, I need to display a popup message when some validation is not the right one.

The thing is that my message is working only after I push the “submit” button two times. The first time just the page is reload, and if I push the button again, the popup do appear!

EDIT: I just forget to add some details. I’m using VS 2010, building a Web Application asp.net with C# as code behind.

public partial class Barcode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            Validate();

            if (IsValid)
            // 
            {
                string kemet = kemetTextBox.Text;
                string sud = sudTextBox.Text;

                if (kemet.Length == 14 && sud.Length == 28) // SOME VALIDATION CONTROL
                {

                    if (kemet.Substring(1) == sud.Substring(0, 13) && kemet != "" && sud != "")
                    {

                        //resultLabel.Text = "HIGH VOLUME<br/>";
                        redImage.Visible = false;
                        greenImage.Visible = true;

                    }
                    if (kemet.Substring(1) != sud.Substring(0, 13) && kemet != null && sud != null)
                    {

                        //  resultLabel.Text = "LOW VOLUME<br/>" + kemetEd + sudEd;
                        greenImage.Visible = false;
                        redImage.Visible = true;
                    }
                }
                else
                    Button1.Attributes.Add("onClick", "javascript:alert('Message Here');"); // HERE WOULD BE THE ERROR MSG 

I try to make the IsPostBack false, but that just made it worse.

thank you!

Answer 1

Try replacing this:

Button1.Attributes.Add("onClick", "javascript:alert('Message Here');");

By this:

RegisterDOMReadyScript("alert message", "alert('Message Here');");

Which uses the following helper methods:

public void RegisterDOMReadyScript(string key, string script)
{
    string enclosed = EncloseOnDOMReadyEvent(script);
    ScriptManager.RegisterClientScriptBlock(this, this.GetType(), key, enclosed, true);
}

private string EncloseOnDOMReadyEvent(string str)
{
    StringBuilder sb = new StringBuilder();
    sb.Append("function r(f){/in/.test(document.readyState)?setTimeout('r('+f+')',9):f()} r(function(){")
        .Append(str)
        .Append("});");
    return sb.ToString();
}

This will make sure your message will only be displayed after the document is ready, preventing ugly formatting issues.