Oracle datatypes vs .NET datatypes

Hi! Does anyone know how to make a data type conversion from Oracle database data to a .Net data type upon filling a DataSet ? Here is my situation. I would like to define a schema within a WinForm application in C# in order to do disconnected validation against it before sending changes to the database server. I supposed that I could define every column type of my tables. However, the database already contains data. So when I try to set the DataType for a column after filling the DataSet, I get an exception telling me that I can't define DataType for columns that already contains data. But if I try to define a DataTable on my own and to specify DataType for each column before filling the DataSet, then my DataTable doesn't seem to get filled with database data. I'm trying to find a way to convert data types I get from database, also because I need to show some values in CheckedBoxes. It happens that the database I deal with has defined some status field with values 0 or 1 of char type of length 1. I don't know how to handle the fact that CheckBoxes takes true or false to define its Checked state. The binding on attribute Checked of the CheckBox simply doesn't work because Oracle char type is converted as System.String by default when DataSet is filled up. Does anyone can help me or point me to explicit documentation on the subject ? Thanks, Friedryk (this is a new post)