/// <summary>
/// Iterator to pass data back to calling form via a delegate
/// </summary>
/// <param name="ct">CancellationToken</param>
/// <returns></returns>
public IEnumerable <object[]> LoadCustomers(CancellationToken ct)
{
int RecordCount = this.RowCount();
Person personArray = new Person();
// prepare our delegate
CustomersForm.UpdateDataTableDelegateProgress updateDelegate =
delegate(int CurrentPosition, int Total, Person[] person)
{
callingForm.UpDateDataTable(CurrentPosition, Total, person);
};
using (OleDbConnection cn = new OleDbConnection {
ConnectionString = Builder.ConnectionString
})
{
using (OleDbCommand cmd = new OleDbCommand {
CommandText = "SELECT Identifier, FirstName, LastName FROM People;", Connection = cn
})
{
cn.Open();
OleDbDataReader Reader = cmd.ExecuteReader();
if (Reader.HasRows)
{
while (Reader.Read())
{
personArray.Identifier = Reader.GetFieldValue <int>(0);
CurrentIdentifier = personArray.Identifier;
personArray.FirstName = Reader.GetFieldValue <string>(1);
personArray.LastName = Reader.GetFieldValue <string>(2);
ItemArray = new Person[] { personArray };
// return data to calling form
yield return(ItemArray);
// invoke calling form delegate
updateDelegate(this.CurrentIdentifier, this.RowCount(), ItemArray);
}
}
}
}
}
/// <summary>
/// Checks if a given field (column) in the database is null at the record with the given username.
/// </summary>
/// <param name="studentNumber">The student number to query.</param>
/// <param name="field">The field/column in the database to check if currently null or not.</param>
/// <returns>
/// True if the record returns null for the given student number or if the field at the record
/// with the given student number is null. Returns false if otherwise.
/// </returns>
private bool IsFieldNullAtSUNumber(string studentNumber, string field)
{
String query = "SELECT " + field + " FROM " + TABLE_NAME + " WHERE " + STUDENT_NO_COL + "='" + studentNumber + "';";
OleDbCommand command = new OleDbCommand(query);
try
{
using (OleDbConnection connection = new OleDbConnection(this.connString))
{
// Set the Connection to the new OleDbConnection.
command.Connection = connection;
connection.Open();
OleDbDataReader reader = command.ExecuteReader();
// Open the connection and execute the insert command.
try
{
// Always call Read before accessing data.
reader.Read();
if (reader.GetFieldValue <Object>(0) != DBNull.Value)
{
return(false);
}
else
{
return(true);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
return(true);
}
finally
{
// Always call Close when done reading.
reader.Close();
}
// The connection is automatically closed when the
// code exits the using block.
}
}
catch (Exception)
{
return(true);
}
}
