Developing Database Applications with the Microsoft .NET Framework Cary Jensen Jensen Data Systems, Inc.

1. Developing Database Applications with the Microsoft .NET FrameworkCary JensenJensen Data Systems, Inc.

2. Data Access in Delphi 2005 for .NET • BDE.NET • dbExpress.NET • dbGO (ADO for .NET) • MyBase.NET • IBExpress.NET • DataSet Client for .NET • ADO.NET • BDP.NET

3. BDE.NET dbExpress.NET dbGo (ADO for .NET) ClientDataSets IBX.NET DataSnap .NET Client Third-Party VCL for .NET Datasets ADO.NET BDP.NET Third-Party .NET Data Providers VCL.NET vs ADO.NET VCL.NET ADO.NET

4. BDE Advantages • If you already have it installed and working for existing applications, new applications require little or no configuration to use it. • Many legacy applications exist which use it. • Two or more applications written in Delphi can easily share global aliases. • It has relatively good performance across a large number of data types • It provides access to installed ODBC drivers • Available for Windows and .NET

5. BDE Limitations • In the typically deployment of BDE-based applications, a copy of the BDE must be installed and configured on each workstation (a network installation is possible, but requires manual registry configuration) • The BDE is somewhat inefficient, in that it stores as many as three copies of table metadata • When used with local tables such as Paradox tables, failure to correctly configure the BDE can produce periodic index corruption • If a new BDE application is incorrectly installed, existing BDE applications may fail to initialize properly • Not available for Linux • Borland SQL Links for Windows have been deprecated

6. dbExpress Advantages • Data-related operations in dbExpress tend to be faster than the BDE • dbExpress-based applications can be deployed on Win32, .NET, and Linux platforms • Applications designed to use dbExpress can more easily be ported to using DataSnap • dbExpress applications require fewer support files and can require far less configuration than BDE applications

7. dbExpress Limitations • dbExpress applications are generally more complicated than other types of Delphi database applications to program. In addition to requiring more components to access and edit data, dbExpress applications generally require more lines of code than non-dbExpress applications • No equivalent to midaslib, dbexpint units. Must deploy midas.dll, dbexpint.dll, dbxintf.dll, etc. • There are few dbExpress drivers currently available. • Information about deploying dbExpress application compiled using Delphi 8 is scarce

8. MyBase.NET Advantages • ClientDataSet applications have minimal installation requirements • The data can be stored in XML format, making it easy to access this data from outside of the application • Data can be loaded and saved without code. Simply point the ClientDataSet's FileName property to a file that contains the proper XML or binary client dataset data, and it will take care of the rest. (It is better to explicity load and save using SaveToFile and LoadFromFile.) • Available in Windows, .NET, and Linux

9. MyBase Limitations • Because the records in a client dataset are stored in-memory, the number of records that you can load is limited by the amount of real and virtual memory available on your machine • Large files may take a significant amount of time to load from a file into a client dataset • ClientDataSet applications are limited to single user applications. If you want to create a multiuser application, you must use one of the other available technologies • Requires the deployment of additional DLLs (midas.dll, …)

10. dbGo (ADO for .NET) Advantages • Any Windows-based computer shipped in the past few years already has MDAC installed. As a result, most ADO-based applications require only the installation of the specific OLE DB provider, at most. • ADO can be used from a wide range of development environments, including MS Access, VisualBasic, Delphi, Visual C++, to name of few. • A wide range of OLE DB providers are available.

11. dbGo (ADO for .NET) Limitations • While MDAC is available on many machines, it is not available on all (for example, Windows 95 machines do not have MDAC installed by default). These machines must have MDAC (and DCOM) installed before an ADO-enabled application can run • ADO is available only for the 32-bit Windows operating system • Having MDAC installed and configured is not enough. In some cases, you must also install and register an appropriate OLE DB provider • Performance using ADO is largely reliant on the quality of the OLE DB provider that you are using • Applies to VCL.NET only • If you are using the OLE DB provider for ODBC, an appropriate ODBC driver must also be installed and configured

12. InterBase Express Advantages • InterBase Express provides access to InterBase without the BDE • Because InterBase Express components are designed specifically for InterBase, they include a number of specialized components that access and leverage InterBase features • Interbase Express components are available for Windows, .NET, and Linux

13. InterBase Express Limitations • InterBase Express works only with the InterBase database server

14. DataSnap Advantages • DataSnap client applications have few installation requirements • Business rules can be implemented on a server, permitting these rules to be updated independent of the individual client applications • They provide a reliable, distributed upgrade path to dbExpress and MyBase applications

15. DataSnap Limitations • While DataSnap offers additional flexibility over traditional client/server solutions, it requires more development. Specifically, in addition to writing the client application, you also need to write the application server. • Cannot write DataSnap servers in Delphi 8 • Delphi 8 only supports DCOM connections • Delphi 8 does not support load balancing or fail-over • DataSnap applications require an additional license before they can be deployed. This license can be found in the Enterprise edition of Delphi. • DataSnap servers must also employ one of the other data access mechanisms • As with other ClientDataSet examples, you must deploy midas.dll.

16. Advantages of Third-Party Data Access Mechanisms • They likely provide optimized access to a particular file type or database server. • They may support the familiar TDataSet interface. • They are likely to provide support for proprietary database features. • As is the case with the Advantage TDataSet Descendant for Delphi 8, they may provide cross-platform support

17. Limitations Third-Party Data Access Mechanisms • They likely support only one vendor's database • You must rely on the producer of the third-party data access mechanism to stay current with Borland technologies

18. Advantages of ADO.NET • Supported by all first-class .NET languages • Native to the FCL • Results in smaller executables • Works with third-party .NET data providers • Powerful in-memory DataSets • Tight integration with XML

19. Limitations of ADO.NET • Only for the .NET platform • Compared with TDataSet.NET solutions, sports a different interface from previous Delphi implementations • When using with third-party .NET data providers, requires the deployment of additional assemblies • Different type namespaces for different .NET data providers

20. Advantages of BDP.NET • Portable code : Write once and connect to all supported DB’s • Open Architecture: Lets you add support to more DB’s easily • Logical Data types mapped to .NET Native types • Consistent data type mapping across DB’s • Unlike OLEDB .NET Provider, no need to go through a COM interop layer. • Support for Database specific features • Live, Delphi-like design-time data views • Valuable component editors

21. Limitations of BDP.NET • Yet another proprietary data access mechanism • Requires the installation of additional assemblies into the global assembly cache • There are few BDP.NET supported databases • Uses the ADO.NET interfaces as opposed to the TDataSet interfaces • Current design-time code generation is aggressive, providing more features than you may want • Not supported on Win32 or Linux platforms

22. ADO.NET Major Interfaces and Classes DataSet DataTableCollection IDbDataAdapter DataRelationCollection IDataReader DataTable DataRowCollection IDbCommand DataColumnCollection IDbParameter DataRow DataColumn IDbConnection DataRelation DataView Database Constraint DataRowView XML Document

23. DataSets, DataTables, and DataRows var Table: DataTable; Row: DataRow; data: String; begin Table := DataSet1.Tables[0]; Row := Table.Rows[2]; data := Row[1].ToString(); DataSet Table1 Table2

24. DataSets, DataTables, and DataRows var data: String; begin data := DataSet1.Tables[0].Rows[2][1].ToString() DataSet Table1 Table2

25. Controls and CurrencyManagers • All controls, that is, classes that descend from Control in the .NET FCL, are data aware, and can be bound to a data source. A BindingManagerBase instance is created anytime a control is bound to a new data source. • Controls that are bound to the same data source are bound to the same BindingManagerBase instance. BindingManagerBase is an abstract class, and two concrete classes descend from it. These concrete classes are CurrencyManager and PropertyManager.

26. Creating a Data Module • Create a form that will serve as the data module (let’s call this form the data module) Add the ADO.NET components that you want to share to the public section of the data module's class declaration. • When the data module is created, create the instances of, and configure, the ADO.NET classes that you added to the form's public section • Add one Control descendant to the data module for each data source that you want to use in other forms. Bind each control to the data source you want to expose. • Declare a variable of the data module class type within scope of each form that must use a data module data source • For each form that uses the data module, assign that form’s BindingContext property to the data module's (form-level) BindingContext property. • For each Control descendant on each form, set the binding context (or DataSource and DataMember properties) to the appropriate data source on the data module.

27. Field References in Expressions • Use the ColumnName property to reference fields • if ColumnName contains one of the following characters, the field reference must be enclosed in brackets: (space), \n (newline), \t (tab), \r (carriage return), ~, (, ), #, \, /, =, >, <, +, -, *, %, &, |, ^, ‘, “, [,] • For consistency, you can use brackets even when the column name does not include one of the special characters. • If your column name includes the ] character, it must be preceded by a \.

28. Column Name AccountNo Account# Last Name Column[1] Reference AccountNo [Account#] [Last Name] [Column[1\]] Field Reference Examples

29. Literals • Strings enclosed in single quotesex: 'Mr ' + [Contact Name] • Dates enclosed between # characters:ex: [Date] - #1/1/2004# • Numeric values, including decimal values and scientific notation, are not delimitedex: [Percent] * 100

30. String Literals and Delphi • Consider the following string assignment (in C#):dataColumn1.Expression = "'Mr ' + [First Name] + ' ' + [Last Name] "; • String literals are more complicated for Delphi developers, since single quotes are already used to delimit strings. For example: DataColumn1.Expression := '''Mr ''' + ' + [First Name] + ' + ''' ''' + ' + [Last Name]'; • You can also use the QuotedStr function in Borland.Vcl.SysUtils: DataColumn1.Expression := QuotedStr('Mr ') + ' + [First Name] + ' + QuotedStr(' ') + ' + [Last Name]'; • Alternatively, enclose string literals between #39, like this: DataColumn2.Expression := #39 + 'Mr ' + #39 + ' + [Invoice No] + ' + #39 + ' ' + #39 + ' + [Customer ID]'; • You can even omit the concatenation operator (+) between #39 and strings: DataColumn2.Expression := #39'Mr '#39' + [Invoice No] + '#39' '#39' + [Customer ID]';

31. Comparison operators (in order of precedence) < > <= >= <> = IN LIKE

32. Boolean Operators • ( expression) • AND • OR • NOT

33. Programmatically Create Calculated Fields • Create a DataColumn in your DataTable that will hold the calculated field • After loading data, iterate through the DataTable and assign the calculation. Then make the calculated field to readonly • Add a ColumnChanged event handler to the DataTable • From the ColumnChanged event handler, test whether the changed field is one of those involved in the calculation. If so, make the calculated field writeable, re-calculate the calculation, then make the field readonly once again

35. DataSync and DataHub • New components introduced in Delphi 2005 • Provide a richer mechanism for data handling • Works with both ADO.NET data providers and BDP for .NET data providers • Permit live views of data at design time • Provide a migration path for remote data access

36. DataSync and DataHub

37. RemoteServer and RemoteConnection • Provide automatic .NET remoting for .NET datasets • Add a RemoteServer to an application • Connect the RemoteServer to that application’s DataSync • Add a RemoteConnection to a client application • Connect the RemoteConnection to a DataHub to provide it with access to the DataSync on the server

38. RemoteServer and RemoteConnection

39. Thank You !