The ModalPopup Extender Allow a page to display content to the user in a "Modal" manner which prevent the user from interacting with the rest of the page.

CSS Coding for Popup Background

.modalBackground { 

            background-color:#333333; 

            filter:alpha(opacity=70); 

            opacity:0.7; 

        } 

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Important Properties of ModalPopupExtender

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PopupControlID="Panel1" 

TargetControlID="Button1" 

OkControlID="Button2" 

CancelControlID="Button3" 

BackgroundCssClass="modalBackground"

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PageLoad Coding

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Panel1.Style.Value = "display:none;";

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Button Click Event Coding

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Label4.Text = "You Have Voted For : "+RadioButtonList1.SelectedItem.Text;

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Set OkButton Property

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UseSubmitBehavior="False"