Use the following on .aspx page:-
<asp:GridView ID="GridView1" runat="server" AllowPaging="True"
AutoGenerateColumns="False" DataKeyNames="isdeleted"
DataSourceID="SqlDataSource1" onrowdatabound="GridView1_RowDataBound">
<Columns>
<asp:CheckBoxField DataField="isdeleted" HeaderText="isdeleted"
SortExpression="isdeleted" />
<asp:BoundField DataField="tasktype_name" HeaderText="tasktype_name"
SortExpression="tasktype_name" />
<asp:BoundField DataField="tasktype_id" HeaderText="tasktype_id"
InsertVisible="False" ReadOnly="True" SortExpression="tasktype_id" />
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:YourConnectionString %>"
SelectCommand="SELECT [isdeleted], [tasktype_name], [tasktype_id] FROM [TaskType]">
</asp:SqlDataSource>
and below is code in RowDataBound to check that checkbox is already checked then show in different color -
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
bool checkFlag =Convert.ToBoolean (GridView1.DataKeys[e.Row.RowIndex].Value);
if (checkFlag==true)
{
e.Row.BackColor = System.Drawing.Color.Black;
}
}
}