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ASP.NET CausesValidation="True" does nothing

I have a form with Required field validator controls to validate if the control is empty or not. I put the CausesValidation="True" in the submit button to prevent the form from saving data if there's required field empty and give an appropriate error message.
However, whenever I click submit, nothing happened: NO error message and the form is not saved either.It just stays there without any event occurring.
Also, i noticed even ALL required fields are correctly filled up, it still does nothing upon submitting, unless if I put the CausesValidation="False", then only I am able to submit the form (but no validations take place, which is not what I want).
here's my code:
My Control to validate:
<asp:TextBox runat="server" ID="TxtCostCenter" Text='<%# Bind("CostCenter") %>' MaxLength="254"
Size="254" SkinID="InputBox" />
<asp:RequiredFieldValidator ID="RfvTxtCostCenter" runat="server" ControlToValidate="TxtCostCenter"
Display="Dynamic" ErrorMessage="<%$ Resources:WebResources, ErrorFieldIsRequired %>" />
also my Submit button (there are two submit buttons though, 1 is at the top and the other is at the bottom of the page):
top:
<asp:LinkButton ID="LinkInsert" runat="server" ToolTip="<%$ Resources:WebResources, ButtonSave %>"
CausesValidation="true" CommandName="Update">
bottom:
<asp:LinkButton ID="LinkButton2" runat="server" ToolTip="<%$ Resources:WebResources, ButtonSave %>"
CausesValidation="true" CommandName="Update">
I also tried the ValidationGroup="val" but it still does not work.

prevent The Client side validation go to server side

I have a form and I have a validation in JavaScript. How to prevent the submit button go the the server side if the form is not valid?
<button id="LoginButton" onclick="Login.initReuiredValidation();"
onserverclick="LoginButton_Click" runat="server" type="submit"
class="submit btn btn-primary pull-right">
<asp:Literal runat="server" meta:resourcekey="LoginButton" />
<i class="icon-angle-right"></i>
</button>

in jquery you can do as
$(yourform).submit(function(event){
event.preventDefault();
//do somehting
})

This isn't classic asp, it's asp.net webforms and I've edited the tags accordingly
Adding input validation in webforms is quite easy, you can assign a validation control to each form control, eg
Contact Name<br />
<asp:TextBox ID="Contact_name" runat="server" Width="246 pt"></asp:TextBox>
<asp:RequiredFieldValidator ID="ContactNameValidator" runat="server"
ErrorMessage="Please enter your name" ControlToValidate="Contact_name"></asp:RequiredFieldValidator><br />
<br />
Contact Telephone<br />
<asp:TextBox ID="Contact_phone" runat="server" Width="246pt"></asp:TextBox>
<asp:RequiredFieldValidator ID="ContactPhoneValidator" runat="server" ControlToValidate="Contact_phone"
ErrorMessage="Please enter your telephone number"></asp:RequiredFieldValidator>
If you view the output, you will see that the validation is actually done with (client side) JavaScript. Asp.net generates that for you, you don't have to write it yourself.
Further information here
https://msdn.microsoft.com/library/a0z2h4sw%28v=vs.100%29.aspx

In the code behind add...
LoginButton.Attributes.Add("onclick", "return false;");

How to execute event when user presses return on web page

I have an ASP.NET website and I have a forgot password page where the user enters their email address in a text box and when they click the button to retrieve password, the event runs as fine.
Only problem is if the user types in their email address and presses ENTER instead, it runs a search (I have a search bar at the top of the page) and so the result comes back as 'search query not found'. But this search bar at the top is on a different ASP.NET page.
So anyway, I want the event onclick to run when the user presses enter and not run a search query. Does anyone have any ideas? I've searched on this site but not really found the answer I need.

There are couple ways you can do this. If it is a webform and you have your textbox wrapped with an asp:panel you can do as below:
<asp:Panel ID="p" runat="server" DefaultButton="myButton">
<%-- Text boxes here --%>
<asp:Button ID="myButton" runat="server" />
</asp:Panel>
If its not a webform or you want to move away from that try below:
<asp:TextBox ID="TextBox1" runat="server" onkeypress="return EnterEvent(event)"></asp:TextBox>
<asp:Button ID="Button1" runat="server" style="display:none" Text="Button" />
function EnterEvent(e) {
if (e.keyCode == 13) {
__doPostBack('<%=Button1.UniqueId%>', "");
}
}
And in the codebehind fire your button click in the page load based on the parameters of the postback.

Specify the "defaultbutton" property to the ID of (event you want to fire).
You can specify the "defaultbutton" property at the Form level (in the form tag)
Or else you can define them at panel level in the tag.
The form level setting is overridden at the panel level setting.
The Event Handler for the specified button gets fired simulating a true submit button functionality.
<form id="sampleform" runat="server" defaultbutton="button1">
<div>
<asp:TextBox ID="textBox1" runat="server"></asp:TextBox>
<asp:Button ID="button2" runat="server" Text="Cancel" OnClick="Button2_Click" />
<asp:Button ID="button1" runat="server" Text="Ok" OnClick="button1_Click" />
<asp:Panel ID="panel1" runat="server" defaultbutton="Button5">
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox5" runat="server"></asp:TextBox>
<asp:Button ID="Button5" runat="server" Text="Button5" OnClick="Button5_Click" />
</asp:Panel>
</div>
</form>
In this example, Button1 is the default button for the form (Type something in Textbox 1 and hit enter, button1_Click gets fired). But for "Panel 1", default button will be Button 5 (Type in Textbox3 or Textbox 5 and hit enter).
You can have any number of panels with different default button for each panel.

Adding an ASP Panel around the text box and button with the id of the button name as the property for DefaultButton was the best way to do this.
<asp:Panel ID="p" runat="server" DefaultButton="myButton">
<%-- Text boxes here --%>
<asp:Button ID="myButton" runat="server" />
</asp:Panel>

ValidationGroup fired after OnClick

I would like to do client-side validation to check if the textbox is empty before submit the form to server. However, the form is submit to server even though the textbox is empty.
<asp:Button ID="LinkButton2" runat="server" Text="Submit Order" CssClass="btn btn-lg btn-primary btn-block"
ValidationGroup="DeliveryAddVad" OnClick="SbmtOrder_Click" Width="150px" />
An error message will display under the textbox.
Is there anyway can stop the form submit to server if the textbox is empty.
The concern is OnClick="SbmtOrder_Click" will display a dialog, I do not want the dialog to show up if the textbox is empty.

You have to use a RequiredFieldValidator:
<asp:Button ID="LinkButton2" runat="server"
ValidationGroup="DeliveryAddVad"
UseSubmitBehavior="False"
Text="Submit Order"
CssClass="btn btn-lg btn-primary btn-block"
OnClick="SbmtOrder_Click"
Width="150px"
/>
<asp:RequiredFieldValidator runat="server" ID="reqOrder"
ValidationGroup="DeliveryAddVad"
controltovalidate="NameOfTextBox"
errormessage="Please enter [whatever the user has to enter]!"
/>
You can also try to set Button.UseSubmitBehavior to false (edited above) and the TextBox.CausesValidation to true(default false).

Tries to validate when pressing logout button instead of submit

On my admin pages I've got a "Log out" button. On one page there's this form you can fill in and submit and it has some validator controls. The problem is that when I am on this page, I can't log out, because it wants the textboxes to be filled in, even though it's - obviously - not submitted via the log out button. Are the validators executing everytime you try to leave this page, even though I'm not trying to submit a form? To be clear: it works for every other page, it's just the validation here that stops it.
Form code:
<p>
<asp:Label ID="lblA" runat="server" Text="LabelA"></asp:Label><br />
<asp:TextBox ID="txtA" runat="server"></asp:TextBox>
*
<asp:RequiredFieldValidator
ID="rfvA"
runat="server"
ControlToValidate="txtA"
ErrorMessage="Required"
Display="Dynamic">
</asp:RequiredFieldValidator>
</p>
<p>
<asp:Label ID="lblB" runat="server" Text="LabelB"></asp:Label><br />
<asp:TextBox ID="txtB" runat="server"></asp:TextBox>
*
<asp:RequiredFieldValidator
ID="rfvB"
runat="server"
ControlToValidate="txtB"
ErrorMessage="Required"
Display="Dynamic">
</asp:RequiredFieldValidator>
</p>
Logout button:
<asp:Button runat="server" Text="Log out" ID="btnLogout" OnClick="btnLogout_Click"/>
When Log out is clicked:
protected void btnLogout_Click(object sender, EventArgs e)
{
FormsAuthentication.SignOut();
FormsAuthentication.RedirectToLoginPage();
}
Any ideas?

add cause validation false to your button
<asp:Button runat="server" CausesValidation="False" Text="Log out" ID="btnLogout" OnClick="btnLogout_Click"/>

Also you can use the ValidationGroup property of the controls.
Assign the same ValidationGroup to the group of controls(and RequiredFieldValidator) which you require for validation like username and password text boxes and login button(In your case to the two text boxes) and assign the different ValidationGroup to the other controls(In your case to logout button).
So the validation fires only when the same validation group's button has been clicked.