Set AutoPostBack="True" with your CheckBox control.
<asp:ImageButton ID="imgs" runat="server" ImageUrl="images/-trash.png" OnClick="imgs_Click" Width="40px" Height="40px" />
<asp:CheckBox ID="item_check" runat="server" OnCheckedChanged="item_check_CheckedChanged" AutoPostBack="True" />
protected void item_check_CheckedChanged(object sender, EventArgs e)
{
if (item_check.Checked)
imgs.Enabled = true;
else
imgs.Enabled = false;
}
Do the same check on Page Load
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
if (item_check.Checked)
imgs.Enabled = true;
else
imgs.Enabled = false;
}
}