System.Data.Odbc.OdbcDataReader.OdbcDataReader.GetPrimaryKeysBySQLStatistics C# (CSharp) Method

		private unsafe ArrayList GetPrimaryKeysBySQLStatistics (string catalog, string schema, string table)
		{
			ArrayList keys = new ArrayList ();
			IntPtr handle = IntPtr.Zero;
			OdbcReturn ret;
			try {
				ret=libodbc.SQLAllocHandle(OdbcHandleType.Stmt, 
							   command.Connection.hDbc, ref handle);
				if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo))
					throw Connection.CreateOdbcException (
						OdbcHandleType.Dbc, Connection.hDbc);

				ret = libodbc.SQLStatistics (handle, catalog, -3,  
							     schema, -3, 
							     table, -3,
							     libodbc.SQL_INDEX_UNIQUE,
							     libodbc.SQL_QUICK);
				if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
					throw Connection.CreateOdbcException (OdbcHandleType.Stmt, handle);

				// NON_UNIQUE
				int  nonUniqueLength = 0;
				short nonUnique = libodbc.SQL_FALSE;
				ret = libodbc.SQLBindCol (handle, 4, SQL_C_TYPE.SHORT, ref nonUnique, sizeof (short), ref nonUniqueLength);
				if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
					throw Connection.CreateOdbcException (OdbcHandleType.Stmt, handle);

				// COLUMN_NAME
				int length = 0;
				byte [] colName = new byte [255];
				ret = libodbc.SQLBindCol (handle, 9, SQL_C_TYPE.CHAR, colName, colName.Length, ref length);
				if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
					throw Connection.CreateOdbcException (OdbcHandleType.Stmt, handle);
			
				while (true) {
					ret = libodbc.SQLFetch (handle);
					if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
						break;
					if (nonUnique == libodbc.SQL_TRUE) {
						string pkey = Encoding.Default.GetString (colName, 0, length);
						keys.Add (pkey);
						break;
					}
				}
			} finally {
				if (handle != IntPtr.Zero) {
					ret = libodbc.SQLFreeStmt (handle, libodbc.SQLFreeStmtOptions.Close);
					if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo))
						throw Connection.CreateOdbcException (OdbcHandleType.Stmt, handle);

					ret = libodbc.SQLFreeHandle ((ushort) OdbcHandleType.Stmt, handle);
					if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo))
						throw Connection.CreateOdbcException (OdbcHandleType.Stmt, handle);
				}
			}
			return keys;
		}