Question

I read data from MS Access using C#. But get the OleDbException trying to execute such query:

SELECT * FROM Flats  WHERE Flats.VersionStamp <= [theDate] AND Flats.Flat=[theFlat] 

OleDbException:

Data type mismatch in criteria expression. 

On the other side, any one of the following queries works fine:

SELECT * FROM Flats  WHERE Flats.VersionStamp <= [theDate] AND Flats.Flat=1  SELECT * FROM Flats  WHERE Flats.VersionStamp <= #1/1/2009# AND Flats.Flat=[theFlat] 

The C# code stays the same all the time:

DbParameter theFlat = new OleDbParameter('theFlat', 1); DbParameter theDate = new OleDbParameter('theDate', new DateTime(2009, 1, 1));  using (DbDataReader reader = dbHelper.ExecuteReader(sqlText, theFlat, theDate)) { } 

Finally, the query can be successfully executed directly in the MS Access UI.

What is wrong here?

Answer 1

I am not sure but I don’t think the OleDb classes support named parameters. Try the following SQL instead:

SELECT * FROM Flats WHERE Flats.VersionStamp <= ? AND Flats.Flat=? 

The parameters must be added to the command object in the right order (I don’t see you adding the parameters in your code).