private void AddColumnsConditionsByCode() {

    query1.Clear();

    EntityAttr attr;
    attr = dataModel1.EntityRoot.FindAttribute(EntityAttrProp.Expression , "Customers.Country");

    //create columns
    Column col;
    col = new DbColumn("Country", SortDirection.Ascending);
    col.Expr = new DbEntityAttrExpr(dataModel1, attr);
    query1.Columns.Add(col);

    attr = dataModel1.EntityRoot.FindAttribute(EntityAttrProp.Expression, "Orders.Freight");
    col = new DbColumn("Total sum", SortDirection.None);
    col.Expr = new DbAggrFuncExpr(dataModel1, "SUM", new DbEntityAttrExpr(dataModel1, attr));
    query1.Columns.Add(col);

    //create conditions
    //here we create condition object
    SimpleCondition cond = new DbSimpleCondition(dataModel1);

    //then we search for an entity attribute which will be used in the left side of condition
    attr = dataModel1.EntityRoot.FindAttribute(EntityAttrProp.Expression, "Orders.OrderDate");

    //after that we add found entity attribute as first (left side) expression of our condition
    cond.BaseExpr = new DbEntityAttrExpr(dataModel1, attr);

    //here we set an operator used in condition. In our case it will be  "is less than" (< symbol in SQL syntax)
    cond.Operator = dataModel1.Operators.FindByID("LessThan");

    //finally we set the rigth side expression which is some constant value in our case.
    cond.SetValueExpr(1, new ConstExpr(DataType.Date, "2005-01-01"));
    cond.ReadOnly = true;
			
    //when all parts of our condition are ready - we add it to query
    query1.Root.Conditions.Add(cond);
    
    //here is more simple and quicker way to add a condition (same attribute, operator and value)
    query1.Root.AddSimpleCondition("Orders.OrderDate", "DateBeforePrecise", "2005-01-01");

     
     //generate SQL statement
     SqlQueryBuilder builder = new SqlQueryBuilder(query1);
     builder.BuildSQL();
     string sql = builder.Result.SQL;

 }