You can use the required field validator to specify that the cell requires a value.

A validation error occurs if the value is not valid. You can also create an action, such as adding a backcolor to the cell, that lets the user know the value is invalid.

Use the RequiredFieldValidator class to create the validator. Specify a notification type such as CellStyleNotify. Then use the AddValidators method to add the validator to a cell range.

The following image displays a cell with an invalid, empty value.

Using Code

The following example displays the invalid color if the value is deleted from the cell.

//Cell 1,1 requires a value
FarPoint.Win.Spread.CellStyleNotify cnotify = new FarPoint.Win.Spread.CellStyleNotify();
cnotify.InvalidCellStyle.BackColor = Color.Fuchsia;
FarPoint.Win.Spread.RequiredFieldValidator requiredv = new FarPoint.Win.Spread.RequiredFieldValidator();
requiredv.Actions.Add(cnotify);
fpSpread1.Sheets[0].AddValidators(new FarPoint.Win.Spread.Model.CellRange(1, 1, 1, 1), requiredv);
fpSpread1.Sheets[0].Cells[1, 1].Text = "Value";

'Cell 1,1 requires a value
Dim cnotify As New FarPoint.Win.Spread.CellStyleNotify()
cnotify.InvalidCellStyle.BackColor = Color.Fuchsia
Dim requiredv As New FarPoint.Win.Spread.RequiredFieldValidator()
requiredv.Actions.Add(cnotify)
fpSpread1.Sheets(0).AddValidators(New FarPoint.Win.Spread.Model.CellRange(1, 1, 1, 1), requiredv)
fpSpread1.Sheets(0).Cells(1, 1).Text = "Value"