Table is nullable DateTime, but DataSet throws an exception?

Thanks this solved my similar issue : Here is the code. In case of this question

Isevent_start_date()

would return whether or not the field is null.

In my case: I had a similar problem and I used the following solution

            //Table's Name is Efforts,
            //Column's name is Target
            //So the dataset would automatically generate a property called IsTargetNull() which can be used to check nullables
            //Create an Adaptor
            EffortsTableAdapter ad = new EffortsTableAdapter();
            ProjectDashBoard.Db.EffortsDataTable efforts = ad.GetData();
            DataColumn targetColumn = new DataColumn();
            targetColumn = efforts.TargetColumn;

            List<DateTime?> targetTime = new List<DateTime?>();
            foreach (var item in efforts)
            {

                //----------------------------------------------------
                //This is the line that we are discussing about : 
                DateTime? myDateTime = item.IsTargetNull() ? null : (DateTime?)item.Target;
                //----------------------------------------------------

                targetTime.Add(myDateTime);

            }

Typed data sets don't support nullable types. They support nullable columns.

The typed data set generator creates non-nullable properties and related methods for handling null values. If you create a MyDate column of type DateTime and AllowDbNull set to true, the DataRow subclass will implement a non-nullable DateTime property named MyDate, a SetMyDateNull() method, and an IsMyDateNull() method. This means that if you want to use a nullable type in your code, you have to do this:

DateTime? myDateTime = myRow.IsMyDateNull() ? null : (DateTime?) row.MyDate;

While this doesn't totally defeat the purpose of using typed data sets, it really sucks. It's frustrating that typed data sets implement nullable columns in a way that's less usable than the System.Data extension methods, for instance.

Is particularly bad because typed data sets do use nullable types in some places - for instance, the Add<TableName>Row() method for the table containing the nullable DateTime column described above will take a DateTime? parameter.

Long ago, I asked about this issue on the MSDN forums, and ultimately the ADO project manager explained that nullable types were implemented at the same time as typed data sets, and his team didn't have time to fully integrate the two by .NET 2.0's ship date. And so far as I can tell, they haven't added new features to typed data sets since then.