not null -> true and null -> false

select 
CASE
 when ImageFile is NULL then 0
 else 1
end as HasImage
from News

Bind to ItemIndex

Repeater:
<% #DataBinder.Eval(Container, "ItemIndex") %>
Gridview:
<% #DataBinder.Eval(Container, "RowIndex") %>

Footer always bottom

HTML:

    <div id="container">
        <div id="main">
            <div id="header">
                <h2>
                    header
                </h2>
            </div>
            <div id="content">
                <h2>
                    content content content content<br />
                    content content content content<br />
                    content content content content<br />
                    content content content content<br />
                </h2>
            </div>
        </div>
    </div>
    <div id="footer">
        <h2>
            footer
        </h2>
    </div>

CSS:

*{padding:0; margin:0;}
html {height: 100%;}
body {height: 100%;}
#container {min-height: 100%;}
* html #container {height: 100%;}
#header {height: 110px;}
#footer {height: 90px;position: relative;margin-top:-90px;}
#main {min-height: 100%;}
* html #main{height: 100%;}
#content {padding-bottom: 90px;}

#header{background:red;}
#container {background:#aaa;}
#content{background:green;}
#footer{background:blue;}

Body min-height 100%

  html
  {
    height:100%;
  }
  body
  {
    margin:0px;
    min-height:100%;
    height:100%;
    height:auto !important;
  }

Div min-height

  #content
  {
    min-height:400px;
    height:auto !important;
    height:400px;
  }

GridView + autopostback CheckBox

в темплейтах колонок прописуємо:

    asp:CheckBox ID="chb1" AutoPostBack="true" 
    key='<%# Eval("ID") %>'
    runat="server" 
    OnCheckedChanged="chb1_CheckedChanged"

а в коді:
    protected void chb1_CheckedChanged(object sender, EventArgs e)
    {
        CheckBox chb = (CheckBox)sender;
        string id = chb.Attributes["key"];
        ...
    }

Validation of ViewState Mac failed

Від цієй проблеми допоможуть наступні параметри розділу pages в web.config:

validateRequest="false"
enableEventValidation="false"
viewStateEncryptionMode ="Never"