Question

I have a datagridview. The dgv’s data source is a ‘ReadOnlyCollection’ of objects. One of the properties of the object in the ‘ReadOnlyCollection’ is a nullable ‘DateTime’. What I’m trying to do is show a blank cell where the ‘DateTime’ is null, but apply a different format to the DateTime column, by doing:

TimeOutColumn.DefaultCellStyle.Format = "MM/dd/yyyy HH:mm";

The only problem is that sets all of my null entries to the DateTime.Min value.

‘history’ is the ReadOnlyCollection.
Here’s the current code:

'DataGridViewTextBoxColumn TimeOutColumn = new DataGridViewTextBoxColumn();
            TimeOutColumn.DataPropertyName = "timeout";
            TimeOutColumn.HeaderText = "Time Out";                

            ddgGHistory.Columns.Add(BadgeTypeIDColumn);
            ddgGHistory.Columns.Add(EmployeeColumn);
            ddgGHistory.Columns.Add(TimeInColumn);
            ddgGHistory.Columns.Add(TimeOutColumn);

            ddgGHistory.DataSource = history

            ddgGHistory.Columns[3].DefaultCellStyle.Format = "MM/dd/yyyy HH:mm";
            ddgGHistory.Columns[3].DefaultCellStyle.NullValue = "";

Answer 1

Since DateTime is a non-nullable object, it must have a value. However, it is possible to make DateTime nullable by declaring it as a nullable DateTime.

The following is a non-nullable datetime, and will always have a value.

 DateTime dt = new DateTime();

However,one can declare it as nullable by adding ? after the type.

DateTime? nullable_dt = new DateTime?();

Assuming that nullable_dt has been set to null, the datagridview will show an empty cell where the value from nullable_dt has been assigned.