public partial class aspnet_Users
    {
        public string IsOnline { get; set; }
    }

dataGrid.ItemSoutce = this.context.aspnet_Users;

<sdk:DataGrid.Columns>
                <sdk:DataGridTextColumn Binding="{Binding UserName}" Header="User Name" IsReadOnly="True"/>
                <sdk:DataGridTextColumn Binding="{Binding IsOnline}" Header="Is Online" IsReadOnly="True"/>
                <sdk:DataGridTextColumn Binding="{Binding MessageCount}" Header="Messages" IsReadOnly="True"/>
            </sdk:DataGrid.Columns>