Why returned OleDbConnection.GetSchema("Columns") has no rows while same code works for OracleConnection?

Question

I've made a utility method to get schema from a db table. In this case Oracle 11 db.

    public static DataTable GetColumnsSchemaTable(DbConnection cnctn, string tableName)
    {
        DataTable schemaTable;

        string[] restrictions = new string[3] { null, tableName, null };
        schemaTable = cnctn.GetSchema("Columns", restrictions);

        /* table name is case sensitive and in XXXX db table names are UPPER */
        if (schemaTable.Rows.Count == 0)
        {
            restrictions = new string[3] { null, tableName.ToUpper(), null };
            schemaTable = cnctn.GetSchema("Columns", restrictions);
        }
        return schemaTable;
     }

This works fine when the cnctn is created with System.Data.OracleClient provider factory. When it's created with System.Data.OleDb provider factory the table has no rows. I have an other utility method to get connection strings:

    public static string GetDbConnectionString(DbConnection cnnctn, string provider, string server, string dbName, string user, string pwd)
    {
        if (cnnctn is OleDbConnection)
        {
            string usedProvider;
            if (provider == null)
                usedProvider = "msdaora";
            else
                usedProvider = provider;

            return string.Format("Provider={0};Data Source={1};User Id={2};Password={3};",
                    usedProvider, dbName, user, pwd);
        }
        else if (cnnctn is System.Data.OracleClient.OracleConnection)
        {
            return string.Format("Data Source={0};User Id={1};Password={2};",
                    dbName, user, pwd);
        }
        else if (cnnctn is Oracle.DataAccess.Client.OracleConnection)
        {
            return string.Format("Data Source={0};User Id={1};Password={2};",
                    dbName, user, pwd);
        }
        else if (cnnctn is SqlConnection)
        {
            return string.Format("Data Source={0}; Initial Catalog={1}; User Id={2}; Password={3};",
                server, dbName, user, pwd);
        }
        return string.Empty;
    }

and the db connection works (i'm deleting rows before trying to get schema). All help will be appreciated.

Thanks & Best Regards - Matti

Answer 1

Ok. I sorted it out. I made this code long time ago only for now deprecated OracleClient and left the possibility to use other connections / provider factories. I didn't remember anymore that the restrictions vary from connection to connection. So the correct usage is:

string[] restrictions = new string[4] { null, null, tableName, null }; 

for OleDbConnection.