Asp button don't postback if

Question

I have a login box, made with jquery with text boxes and then an asp:button, that validates and makes the sessions, like in the code.

I have made that a label appears when the username and password is wrong and you click the asp:button, but because of the post back the login box disappears.

 protected void Button1_Click(object sender, EventArgs e)
{
   Connectons etc...
    cmd.CommandText = "SELECT * FROM Users WHERE Email = @email AND password = @pass";
    cmd.Parameters.Add("@email", SqlDbType.VarChar).Value = username.Text;
    cmd.Parameters.Add("@pass", SqlDbType.VarChar).Value = password.Text;
    conn.Open();
    SqlDataReader reader = cmd.ExecuteReader();
    if (reader.Read())
    {
        Session["user_id"] = reader["user_id"];
        Session["username"] = reader["Username"];
        Session["name"] = reader["Name"];
        Session["password"] = reader["Password"];
        Session["LoggedIn"] = true;
        Session["role"] = reader["Role_id"];
        if (Convert.ToInt32(reader["Role_id"]) == 1)
        {
   Response.Redirect("Admin/default.aspx");
        }

        else
        {
            Response.Redirect("default.aspx");
        }

    }

    else
    {

        Label1.Text = "Login is wrong";

    }

    conn.Close();


}

How do i make the button not post back if the login is wrong?

        <a id="modal_trigger" href="#modal" class="btn btn-default">Log ind</a>

    <div id="modal" class="popupContainer" style="display: none;"> </div>

         $("#modal_trigger").leanModal({
        top: 100,
        overlay: 0.6,
        closeButton: ".modal_close"
    });

Since you're validating the login on the server, it would be impossible for you to prevent a postback (since the user validation doesn't occur until the button is clicked). Do you mean you want to disable the login button for future attempts if the first login is incorrect? — Shannon Holsinger, Sep 27 '16 at 18:00
Also - you want to wrap your conn (and your com) in a USING if you are going to redirect before you close it. — Shannon Holsinger, Sep 27 '16 at 18:02
If you mean you don't want to allow postback if the username or password field is empty, then you use control validators. Just clarify what you wnt and we'll help — Shannon Holsinger, Sep 27 '16 at 18:07
Thanks, that makes sense. I just wish i knew how to make the jquery pop up box stay. — Caroline Olivia, Sep 27 '16 at 18:08
Is it possible that you have a postback condition attached to your login rendering (like if(!isPostBack(renderLogin())? If that is the case, just re-call the method to render the loginbox if the login is incorrect. — Shannon Holsinger, Sep 27 '16 at 18:10
I don't have that, but it makes sense to like call the login box if the login is wrong, after the site reloads. — Caroline Olivia, Sep 27 '16 at 18:14
Yes - something is making the login box appear. Whether that's in JavaScript or C# - that's what you need to find and re-create if the login is wrong — Shannon Holsinger, Sep 27 '16 at 18:15
Yes you do have that -- where is the jquery code to create the box in the first place? — Shannon Holsinger, Sep 27 '16 at 18:22
If you share that I can help you. It's a DIV or a method or code - the box doesn't just appear without something telling it to. — Shannon Holsinger, Sep 27 '16 at 18:22

score 1 · Answer 1 · answered Sep 27 '16 at 18:00

1

In button property add AutoPostBack=False

Note: as per your question it is not clear what you want to achieve but as you have asked how to add autopostback to false , so i gave the above answer. If you want to prevent postback if the login is incorrect then it is not possible because the validation of credential of user happen only after the button is clicked.

answered Sep 27 '16 at 18:00

Vishwa Ratna

5,567
5
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2

*as per your question it is not clear* then make sure you should make it clear first using comments – Divyang Desai Sep 27 '16 at 18:08

score 1 · Answer 2 · answered Sep 27 '16 at 18:10

1

A Postback needs to be called to reach the code you have up there. You could use some ajax to query your db onClick and cause a postback when successful I believe. I don't have an example. sorry.

answered Sep 27 '16 at 18:10

Mike Wight

56
1
4
8

Anyone who has that? – Caroline Olivia Sep 27 '16 at 18:14
http://stackoverflow.com/questions/13117054/how-to-authenticate-username-password-in-jquery-with-asp-net The second answer is a great example. – Mike Wight Sep 27 '16 at 18:21
but you will need to understand how to send and receive json through a post or a get – Mike Wight Sep 27 '16 at 18:22

Shannon Holsinger · Accepted Answer · 2016-09-27T18:59:29.053

Your problem is not in the postback, it's in the fact that you're using a predefined login box that is only rendered when the page is not in postback state. Essentially, the rendering code is assuming that every login will be successful.

To fix this, you need to find where/when/how the predefined login "box" is created, and add the line to recreate it right after your "login incorrect" text.

In this manner, the login "box" will re-appear if the first attempt failed.

 if (Convert.ToInt32(reader["Role_id"]) == 1)
    {
        Response.Redirect("Admin/default.aspx");
    }

    else
    {
        Response.Redirect("default.aspx");
    }

}

else
{

    reDraw = true;
}

//this has page scope (outside all methods)
bool reDraw = false;

private void reDrawLogin(){
      Label1.Text = "Login is wrong";
    //re-render login box to allow for another try
    string myScript = "\n<script type=\"text/javascript\" language=\"Javascript\" id=\"EventScriptBlock\">\n";
    myScript += "style="display: block;visibility:visible"> 
    myScript += "\n\n </script>";
 Page.ClientScript.RegisterStartupScript(this.GetType(), "myKey", myScript, false);
 }

 //in your page_load, add:

 if(isPostBack){
    if(reDraw){
       reDrawLogin();
       reDraw=false;
    }
 }

and don't foret the USING in your CONN and COM!!! Good luck.

It doesn't work. The box still disappear. But thanks, now i at least know what to find out. — Caroline Olivia, Sep 27 '16 at 18:54
It's probably being called too soon. I made changes to my answer. Hope it helps. — Shannon Holsinger, Sep 27 '16 at 18:59

Asp button don't postback if

3 Answers3