c#查询表达式中的语法错误(缺少运算符)

string sqlStatement = "select ID, Checkintime, RoomPrice, OrderNo from Orders where RoomType='" + selectedRoom.Key + "' and RoomNumber=" + selectedRoom.Value + " and Checkintime>="+dateOnly+" and CheckinTime<'"+endingTime+"'"; 
myAccessCommand = new OleDbCommand(sqlStatement, myAccessConn);
OleDbDataAdapter myDataAdapter = new OleDbDataAdapter(myAccessCommand);
myDataAdapter.Fill(myDataSet, "Orders");

我在SQL语句行中有语法错误，但我不确定是什么原因导致语法异常。