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Composing Queries in NDO

5/15/2006 5:30:25 PM

anonymous

20 posts

Composing Queries in NDO

Hi, I'm porting an application with SQL code to NDO. My application has a form in which a user can input one, two or more fields for filtering a query. As soon as the search is started, I want to walk through all controls of the form and create the Where clause dynamically during runtime. Depending on the search criteria the SQL statement can include joins among several tables. Can I do something like that in NDO too? C.R.

5/15/2006 5:42:06 PM

Mirko

109 posts

Re: Composing Queries in NDO

Hi, you can either create a NDO query (this is prefereable for most cases) or you submit a SQL pass-through query. But this brings database dependencies into your application which is normally to be avoided. The SQL query has to return a result set with all columns being defined in the mapping file for the result class. Here is an example: NDOql Query: string query = string.Emtpy; Order.QueryHelper qh = new Order.QueryHelper(); if (includeOrderNumber) query += qh.OrderNumber + Query.Op.Eq + txtOrderNumber.Text + Query.Op.And; if (includeType) query += qh.type + Query.Op.Like + txtType.Text + Query.Op.And; .... and so on // Now remove the redundant AND query = query.Substring(0, query.Length - Query.Op.And.Length); Query q = pm.newQuery(typeof(Order), query, false); IList aufträge = q.Execute(); Sql Query: string query = "SELECT OrderNumber, Typ, ... FROM Orders WHERE "; // Take care of all columns in SELECT that are needed to create an object of type order if (includeOrderNumber) query += "OrderNumber" + Query.Op.Eq + txtOrderNumber.Text + Query.Op.And; if (includeTyp) query += "Typ" + Query.Op.Like + txtTyp.Text + Query.Op.And; .... und so weiter // Now remove the redundant AND query = query.Substring(0, query.Length - Query.Op.And.Length); Query q = pm.newQuery(typeof(Order), query, false, Query.Languge.Sql); IList aufträge = q.Execute(); Hope that helps! Mirko Matytschak

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NDO-Forum postings in english please, if possible.

Developing with NDO

Composing Queri...