Advanced queries on DataSet object using OdbcDataAdapter

[jd6strings]

Nested queries to populate a DataSet using OdbcDataAdapter

The class listed below uses a CSV file and OdbcDataAdapter object to populate a DataSet using a nested query BUT I keep getting an Access Violation exception.
Are nested queries in the SelectCommand() method of the OdbcDataAdapter object not valid? I essentially need to execute this query to populate the DataSet:

SELECT Value,Pressure,Temperature
FROM DewPointValues
WHERE Pressure IN ((SELECT MAX(Pressure)
FROM DewPointValues
WHERE Pressure <= 9.2),
(SELECT MIN(Pressure)
FROM DewPointValues
WHERE Pressure >= 9.2))
AND Temperature IN ((SELECT MAX(Temperature)
FROM DewPointValues
WHERE Temperature <= 92.3),
(SELECT MIN(Temperature)
FROM DewPointValues
WHERE Temperature >= 92.3))


public class DewPoint
{

protected DataSet DewPointValues = new DataSet("DewPointValues");

protected OdbcConnection DewPointValuesConn;

public DewPoint()

{

LoadDewPointValuesFile();

}

publicdouble GetH2OContentValue(double pressure, double temperature)

{

double lookupValue = 0.0;

string query = "SELECT * FROM DewPointValues.csv WHERE Pressure IN ((SELECT MAX(Pressure) FROM DewPointValues.csv WHERE Pressure <= " + pressure + "), (SELECT MIN(Pressure) FROM DewPointValues.csv WHERE Pressure >= " + pressure + "))";

OdbcDataAdapter da = new OdbcDataAdapter();

da.SelectCommand = new OdbcCommand(query, DewPointValuesConn);

da.Fill(DewPointValues, "Values");

DataRow[] foundRows = DewPointValues.Tables["Values"].Select();

if (foundRows.GetUpperBound(0) >= 0)

{

foreach (DataRow row in foundRows)

{

lookupValue += Convert.ToDouble(row["Value"]);

}

}

return lookupValue;

}

privatevoid LoadDewPointValuesFile()

{

System.Reflection.Assembly myAssembly = this.GetType().Assembly;

string path = myAssembly.Location;

path = path.Substring(0, path.LastIndexOf("\\") + 1);

// Connection string for a Text File

string ConnectionString = @"Driver={Microsoft Text Driver (*.txt; *.csv)};DBQ=" + path;



DewPointValuesConn = new OdbcConnection(ConnectionString);



DewPointValuesConn.Open();

}

Any help would be appreciated!!!