News combit Dev Blog

Accessing any .NET Data Source with the Data Providers

Posted: Wednesday, January 14, 2015 | 0 comment(s)
The data provider concept has been around for a couple of years now. We steadily work on extending the list of available data providers and can bind to most any data source by now. Besides the well-known ones, there are also some meta providers that deserve some spotlight.

List & Label 20 ships with more than twenty data providers that can be used to easily bind your reports to the data you require. Some of you might not even have noticed, because a lot of the magic happens under the hood. You can easily assign a SqlConnection instance to the DataSource property and will be presented with all parsable tables from this connection in the Designer. LL simply takes whatever you throw at it and tries to make sense of it. A DataSet, DataViewManager or a simple enumerable object are handled in the same way.

The providers basically fall into four major groups:

  1. Database connectors. We currently do support (in no particular order) Microsoft SQL Server, PostgreSQL, MySql, SQLite, Oracle, Firebird, DB2, Access, generic ADO.NET, OleDB, ODBC, OData and Google BigQuery. Besides, we ship a base class for SQL type data providers (DbConnectionDataProvider) that can be inherited from. This base class provides all the handling required to parse queries, create parametrized queries and translate filters to the database syntax. For some real world code examples how to correctly inherit from this class, we provide the sources to some of the providers on Codeplex.
    A couple of other providers that fall in this group help cover even more data sources. Through cooperation with RSSBus and TasteIT, we are able to support most RSS bus connectors as well as Progress data sources.

  2. File/web based connectors. These cover data from XML, CSV, XLS, JSON and REST sources.

  3. Business objects. The ObjectDataProvider offers thorough support for business objects via reflection. It supports hierarchical data sources (i.e. objects containing lists of objects again), typed and untyped enumerations and even supports more advanced interfaces like ITypedList for typing untyped collections and IBindingListView for sorting. You can just as well use this provider for EntityFramework data sources.

  4. Meta providers. This group is probably the least known one, although you can do really fancy things with these providers. Just keep reading if this sounds interesting.

The providers from group 1-3 are very straight forward and most of the time don't need to be created explicitly. However, as some of the providers have different contructor overloads or offer interesting events it's always a good idea to check out the documentation for your particular provider. For example, a quite frequent support request we receive goes like "I just bound List & Label to my business object, but the designer will not come up". Depending on the complexity of your object, this might be expected behavior: the default constructor of the ObjectDataProvider will set the recursion depth to "10", i.e. all relations are parsed ten levels deep. Think of self-relational objects with some hundred enumerable properties and you can easily wait for a couple of minutes until reflection has done its work here. Enter the explicit contruction of the provider:

ObjectDataProvider provider = new ObjectDataProvider(myBusinessObject, 2);

This will restrict the recursion depth to "2" and the Designer will open up lightning fast. For more fine tuning, the provider also has an event "HandleEnumerableProperty" where you can decide case-by-case if the further recursion should be stopped or not.

The meta providers always need to be constructed explicitly. We currently have 2 ½ of them ;-):

a) DataProviderCollection. This provider allows you to mix different other providers in one data source. This way, you can offer the contents of an Excel sheet and a SQL database in just a few lines of code:
DataProviderCollection collection = new DataProviderCollection();
collection.Add(new XlsDataProvider(@"D:\datasources\Orders.xlsx", true);
collection.Add(new SqlConnectionDataProvider(myConnection));
LL.DataSource = collection;

b) InMemoryDataProvider. This provider wraps other providers in an in memory data base. While this may take a tad more time (the data needs to be read first) it offers entirely new features to otherwise restricted providers. For example, there is no way to sort or (natively) filter a CSV data source. Also, you cannot easily add relations between tables from different providers like a CSV file and an Excel sheet.
Using the InMemoryDataProvider, all you need to do is:

CsvDataProvider csv = newCsvDataProvider(@"D:\datasources\Customer.txt",
XlsDataProvider xls = new XlsDataProvider(@"D:\datasources\Orders.xlsx",

InMemoryDataProvider inmem = new InMemoryDataProvider();
inmem.AddTable(csv, "Customers");
inmem.AddTable(xls, "Orders");
inmem.AddRelation("Customers", "Orders", "CustomerID", "CustomerID");
LL.DataSource = inmem;

c) RemoteDataProvider. This provider is not public yet, however we use it internally for our great new Report Server product. It features the complete wrapping of a provider on the server side, opens up a communication channel to a client and can be used there just as if it was a local data source. We'll probably release this provider with version 21, as we've already seen a couple of requests for this technology. To use a famous developer quote: "it works on my machine" :-).



Author: Jochen Bartlau
Head of Development List & Label

Jochen Bartlau leads the development at combit as Managing Director. He's a Microsoft .NET enthusiast driving innovation & agile project management. The mobile devices geek who used to be a physicist in his first life loves to spend his spare time with his family.


combit Development BlogRSS
What’s this blog for?
A place to share updates about the ongoing development of our products. General musings on the software industry included.
April 2021 (2)
March 2021 (1)
February 2021 (2)
January 2021 (1)
December 2020 (2)
November 2020 (1)
October 2020 (2)
September 2020 (1)
August 2020 (2)
July 2020 (1)
June 2020 (1)
May 2020 (2)
April 2020 (2)
March 2020 (2)
February 2020 (1)
January 2020 (1)
December 2019 (1)
November 2019 (2)
October 2019 (2)
September 2019 (2)
August 2019 (2)
July 2019 (2)
June 2019 (2)
May 2019 (1)
April 2019 (0)
April 2019 (1)
March 2019 (1)
February 2019 (1)
January 2019 (1)
December 2018 (1)
November 2018 (2)
October 2018 (4)
September 2018 (4)
August 2018 (2)
July 2018 (2)
June 2018 (2)
May 2018 (1)
April 2018 (1)
March 2018 (1)
February 2018 (2)
January 2018 (1)
December 2017 (1)
November 2017 (2)
October 2017 (3)
September 2017 (3)
August 2017 (2)
July 2017 (2)
June 2017 (1)
May 2017 (2)
April 2017 (1)
March 2017 (1)
February 2017 (1)
January 2017 (2)
December 2016 (1)
November 2016 (1)
October 2016 (4)
September 2016 (5)
August 2016 (2)
July 2016 (2)
June 2016 (3)
May 2016 (2)
April 2016 (3)
March 2016 (3)
February 2016 (1)
January 2016 (2)
December 2015 (2)
November 2015 (1)
October 2015 (4)
September 2015 (5)
August 2015 (2)
July 2015 (2)
June 2015 (2)
May 2015 (1)
April 2015 (2)
March 2015 (1)
February 2015 (1)
January 2015 (1)
December 2014 (2)
November 2014 (1)
October 2014 (1)
September 2014 (2)
August 2014 (1)
July 2014 (2)
June 2014 (1)
May 2014 (2)
April 2014 (1)
March 2014 (2)
+1 800 256 3608 (toll-free North America only)