Question

I was wondering is it possible to enforce a datatable expression only on
visible columns of a datagridview.

heres a use case.
End User has a DataGridView populated with upto ten columns of Numbers and a Final Column with a total. if the user decided to hide one of these columns (idealy) the expression would change depending on the the visible columns in the datagrid.

thanks for any input.

Answer 1

You’ll need to handle the DataGridView.ColumnStateChanged Event.

In myDataTable, at first you set no Expression.
After the Grid is loaded for the first time, launch recalculateTotalExpression.

void recalculateTotalExpression()
{
   // 0. Create a StringBuilder for your new Expression.
   // 1. Go through each of the columns of your datagridview, except the TotalColumn
   // 2. Foreach Visible DataGridView Column, add the corresponding DataTable column to the expression.
   // 3. Set the Expression to the TotalColumn : TotalColumn.Expression = sb.toString();
}

void MyDataGridView_OnColumnStateChanged(DataGridViewColumnStateChangedEventArgs e)
{
   recalculateTotalExpression();
}