The name 'item' does not exist in the current context

<MudDataGrid T="AppFunctionDTO"             Items="@_appFunctionDTOs"             FilterMode="DataGridFilterMode.ColumnFilterRow"             Dense="true"             Filterable="true"><Columns><MudDataGridColumn T="AppFunctionDTO" Title="#" Width="50px"                           HeaderCellClass="text-center" CellClass="text-center"                           TextAlign="DataGridTextAlign.Center"><CellTemplate Context="item">                @_appFunctionDTOs.IndexOf(item) + 1</CellTemplate></MudDataGridColumn><PropertyColumn Property="x => x.Id" Title="Id" HeaderCellClass="text-center" /><PropertyColumn Property="x => x.Name" Title="Name" HeaderCellClass="text-center" /><PropertyColumn Property="x => x.Url" Title="Url" HeaderCellClass="text-center" /></Columns></MudDataGrid>

I'd like to add a sequential number column (STT) to my data table. My project is built with .NET 7 and uses MudBlazor version 7.16.0.