Question

The data reader named eventreader can be empty and i’m trying to work out an appropriate statement to detect if the datareader contains rows and if the require record exists.

oledbexecute("SELECT [Unit No] FROM UnitOpenAtEvent WHERE [Event ID]='" + strDate + "'");
            eventReader = dbcommand.ExecuteReader();
            for (int i = 0; i < checkboxEvent.Items.Count; i++)
            {
                if (checkboxEvent.GetItemCheckState(i) == CheckState.Checked)
                {
                    if (eventReader["Unit No"] != DBNull.Value)
                    {
                        while (eventReader.Read())
                        {
                            if (eventReader["Unit No"].ToString() == checkboxEvent.Items[i].ToString())
                            {
                                oledbexecute("INSERT INTO UnitOpenAtEvent ([Event ID],[Unit No]) VALUES ('" + strDate + checkboxEvent.Items[i].ToString() + "'");
                                intReader = dbcommand.ExecuteNonQuery();
                            }
                        }
                    }
                    else
                    {
                        oledbexecute("INSERT INTO UnitOpenAtEvent ([Event ID],[Unit No]) VALUES ('" + strDate + checkboxEvent.Items[i].ToString() + "'");
                        intReader = dbcommand.ExecuteNonQuery();
                    }
                }
                else if (checkboxEvent.GetItemCheckState(i) == CheckState.Unchecked)
                {

                   // this is effectively a copy of above
                 }
            }

Answer 1

You can check if the DataReader has any rows using e.g.

if (eventReader.HasRows)

Update:
Following from comment below re: IDataReader…

You could do something like this (shortened to include the most relevant bits for conciseness)

eventReader = dbcommand.ExecuteReader();
bool hasRow = eventReader.Read();
if (hasRow)
{
    for (int i = 0; i < checkboxEvent.Items.Count; i++)
    {
        ...
            ...
            while (hasRow)
            {
                // Code in here to deal with each row
                hasRow = eventReader.Read();
            }
    }
}