I am using proper types. The 2 dates are made up of a StartDate and EndDate:
private DateTime _StartDate, _EndDate;
... public DateTime StartDate { get { return _StartDate; } set { _StartDate = value; } } public DateTime EndDate { get { return _EndDate; } set { _EndDate = value; } } ... dvRowFilter.Append(String.Concat("(", ColName, " >= '", StartDate, "' and ", ColName, " < '", EndDate, "')"));