dotConnect for PostgreSQL Frequently Asked Questions

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What is the difference between the Standard and Professional editions?

The Standard Edition represents a fully-featured ADO.NET data provider with design time support and advanced classes. The Professional Edition adds more classes, tools, technologies, and integration capabilities. The following list briefly enumerates main advantages of Professional Edition.

  • Entity Framework support allows you to employ the latest conceptual technology from Microsoft.
  • LinqConnect support allows you to focus on objects instead of relational data in database application development.
  • PgSqlLoader class serves to load external data into the PostgreSQL database extremely fast.
  • The PgSqlDump class serves to store a database or its parts as a script and to restore database from the generated script.
  • The DataLink class serves for universal cross-form data binding.
  • The powerful PgSqlDataTable component as all-in-one table data access solution.
  • The PgSqlDataSet class allows using typed and untyped provider-specific datasets.
  • DataSet Wizard greatly simplifies process of generating datasets in your application.
  • DataSet Manager and DataSet Editor help managing the datasets.
  • Support for dbMonitor that performs per-component tracing of database events such as SQL statement execution, commit, rollback, etc.
  • Enterprise Library support allows you to take advantage of Data Access Application Block functionality.
  • ASP.NET providers support allows using the data provider in ASP.NET 2.0 provider model.
  • Windows Workflow Foundation support includes PostgreSQL Workflow Instance Store and Workflow Tracking
  • Sync Framework support allows using dotConnect for PostgreSQL for synchronizing PostgreSQL data with other data sources.

To test this functionality use the Trial Edition, which incorporates all aforementioned features.

What is the difference between the Express and Standard editions?

Express Edition is a free data provider with basic connectivity features. Standard Edition represents a fully-featured ADO.NET data provider with design time support and advanced classes.

The following list briefly enumerates main advantages of Standard Edition.

  • The PostgreSQLScript class serves to execute series of SQL statements separated by special symbols
  • The PostgreSQLMonitor class monitors dynamic SQL execution in applications that use dotConnect for PostgreSQL
  • The PostgreSQLDependency class tracks changes on the server
  • The PostgreSQLSelectStatement class represents PostgreSQL SELECT statement
  • Design-time features allow you to move the development process from run time to design time, which is way more comfortable
  • The InterForm technology allows referencing components that reside on different forms of a WinForms application
  • Migration Wizard helps to migrate project to dotConnect for PostgreSQL from Microsoft ODBC and OLEDB data providers.

Installation and deployment

I installed dotConnect for PostgreSQL trial, then I have bought and installed purchased version, but something went wrong.

Make sure you had uninstalled the trial version correctly. There should be no old (trial) assemblies present in your system. Uninstall dotConnect for PostgreSQL and check your Global Assembly Cache and local folders for Devart.* assemblies. Remove all Devart.* files and reinstall dotConnect for PostgreSQL.

How do I upgrade to a newer version of dotConnect for PostgreSQL?

Close all running IDEs and help collections, then run the installation package of the newer version. You will be prompted to uninstall the previous version; agree and then proceed to installing the newer build.

You say, there are sample projects, but I can't find any.

Probably you installed dotConnect for PostgreSQL not in full mode. Please choose Full when installing dotConnect for PostgreSQL. All samples are installed by default in \Program Files\dotConnect\PostgreSQL\Samples folder.

Are there any restrictions for Visual Studio Express editions?

Yes, there are some. First, the provider add-in (and hence menu item) is not available. Second, components are not registered in toolbox automatically (though you can do it manually). Finally, advanced Visual Studio integration (DDEX) is not available, except Microsoft Web Developer Express 2008 and 2010.

How do I deploy my application?

To deploy an application written with dotConnect for PostgreSQL, you need to:

  • deploy the Devart runtime assemblies used by your application;
  • include the technical license resource;
  • in case your application uses provider factories, you also need to expose dotConnect for PostgreSQL to the system.

For the detailed description of each of these steps, please refer to the Deployment and Licensing topics in dotConnect for PostgreSQL help.

How to install dotConnect for PostgreSQL on machine that does not have Visual Studio or Delphi installed?

Choose "Minimal" type when asked by the installer.

How do I upgrade my projects from dotConnect for PostgreSQL 3.xx?

In this release there were some important name changes in the product. Particularly, assemblies, namespaces, invariant name, and some types were changed as follows:
"CoreLab.Data" became "Devart.Data";
"CoreLab.PostgreSQL" became "Devart.Data.PostgreSQL";
"PostgreSQLDirectFactory" became "PostgreSQLProviderFactory";
Invariant name became "Devart.Data.PostgreSQL";

Your projects must be updated to be compatible with dotConnect for PostgreSQL 4.0. Here is the list of files you should update:
*.csproj, *.vbproj - references to assemblies
*.cs, *.vb - namespaces
*.licx - namespaces and assembly names
Web.config - assembly names and web provider types

This is done automatically when you invoke the Upgrade wizard from Visual Studio menu: Tools | PostgreSQL | Upgrade Wizard.

I have received a message that Devart.Data is incompatible...

Devart data providers use a common assembly (Devart.Data.dll), so it is necessary to install compatible providers versions. We release our ADO.NET data providers in a single pack, thus releases from the same date should be compatible. Also, Devart data providers should warn you before installation if an incompatible version of Devart.Data.dll was detected.

I have received the following message - "error 0175: The specified store provider cannot be found in the configuration, or is not valid..". What does it mean and what should I do?

You should put the Devart.Data, Devart.Data.PostgreSQL, and Devart.Data.PostgreSQL.Entity.EF<Version> assemblies in the Bin folder of your application (or place these assemblies in Global Assembly Cache). The <Version> here is the version of Entity Framework used in your application. For Entity Framework v1 the assembly is called Devart.Data.PostgreSql.Entity.EF1.dll, for Entity Framework v4 it is Devart.Data.PostgreSql.Entity.EF4.dll, for Entity Framework v5 or v6 it is Devart.Data.PostgreSql.Entity.EF5.dll or Devart.Data.PostgreSql.Entity.EF6.dll respectively. For Entity Framework Core it is Devart.Data.PostgreSql.Entity.EFCore.dll. Make sure that your application is licensed correctly (take a look at the Licensing article for more information).

Please note that there are three versions of Devart.Data.PostgreSql.Entity.EFCore.dll assemblies for different Entity Framework Core versions - 1.1, 2.2, and 3.1. They are located respectively in \Entity\EFCore, \Entity\EFCore2, and \Entity\EFCore3 subfolders of the dotConnect for PostgreSQL installation folder.

Information about provider registering is available in the Deployment article.

Subscriptions and Upgrades

I have a registered version of dotConnect for PostgreSQL. Will I need to pay to upgrade to future versions?

Since PostgreSQLDirect .NET 3.00, all upgrades to future versions are free to users with an active dotConnect for PostgreSQL Subscription.

Users that have a registration for versions of dotConnect for PostgreSQL prior to PostgreSQLDirect .NET 3.00 can upgrade to dotConnect for PostgreSQL 4.00 to jump in on the Subscription Program.

What are the benefits of the dotConnect for PostgreSQL Subscription Program?

The dotConnect for PostgreSQL Subscription Program is an annual maintenance and support service for dotConnect for PostgreSQL users.

Users with a valid dotConnect for PostgreSQL Subscription get the following benefits:

  • Access to new versions of dotConnect for PostgreSQL when they are released
  • Access to all dotConnect for PostgreSQL updates and bug fixes
  • Product support through the dotConnect for PostgreSQL Priority Support program
  • Notification of new product versions

Priority Support is an advanced product support program which offers you expedited individual assistance with dotConnect for PostgreSQL-related questions from the dotConnect for PostgreSQL developers themselves. Priority Support is carried out over email and has a two business day response policy.

The dotConnect for PostgreSQL Subscription Program is available for registered users of dotConnect for PostgreSQL 3.00 and higher.

Can I use my version of dotConnect for PostgreSQL after my Subscription expires?

Yes, you can. dotConnect for PostgreSQL version licenses are perpetual.

Do I need a new subscription to use dotConnect for PostgreSQL 7?

No, you don't. Provided that you have an active subscription, you will be able to download dotConnect for PostgreSQL 7 from Customer Portal.

Technical Licensing

What is the licensing you use?

dotConnect for PostgreSQL uses .NET component licensing. To build operational application dotConnect for PostgreSQL requires valid license. If no license is available, dotConnect for PostgreSQL does not work.

How to embed license into my application?

Usually you do not have to care about embedding license in your application. When you install dotConnect for PostgreSQL the system is configured so that licensing is done transparently. License is automatically added to project when you place a PgSqlConnection component onto a form.
In some cases you have to manually add license. It is necessary for console applications, class libraries, some ASP.NET applications and existing projects initially built with dotConnect for PostgreSQL version that did not use component licensing, that is, 3.20 and older. For instructions on how to add license manually refer to Licensing topic in dotConnect for PostgreSQL help.

On opening connection I get an exception saying "License not found...". What should I do?

This generally indicates that license information could not be found, or you try to apply it in some way that does not suit the kind of application. For example:

  • File licenses.licx, required for dotConnect for PostgreSQL to function properly, could not be found.
  • File licenses.licx is not added as embedded resource.
  • File App_Licenses.dll not found in ASP.NET applications.

To fix the problem determine type of your application and read corresponding section of "Licensing" topic.

On opening connection I get an exception saying "License not valid...". What should I do?

This means that license information was found but it is incorrect. It usually happens in the following cases:

  1. The project was earlier compiled with old or trial version of dotConnect for PostgreSQL.
  2. File licenses.config used by a class library does not refer to launched executable.
  3. The App_Licenses.dll belongs to other application or needs to be recompiled.
  4. Something's wrong with the operating system or installation of dotConnect for PostgreSQL.

If you encounter one of these problems, do the following (the numbers of actions correspond to the numbers of the problems in the above list):

  1. Delete all files from the bin and obj folders and rebuild the project.
  2. Specify the executable in the licenses.config file.
  3. Rebuild App_Licenses.dll for the current application.
  4. Perform the following steps:
    1. uninstall dotConnect for PostgreSQL;
    2. remove all Devart.* and policy.*.Devart.* files from the GAC;
    3. clear the Program Files\Devart\dotConnect and Program Files\Common Files\Devart\dotConnect folders;
    4. re-install dotConnect for PostgreSQL.

Deployed application worked fine some time, but in some moment it started to say "Sorry, your trial period has expired". But I do not use trial version any more.

Probably you compiled the application with Trial edition of dotConnect for PostgreSQL, and deployed it with assemblies from non-trial version. In this case time limit is actual as well. To eliminate the problem just recompile the project.

How to license ASP.NET applications?

To support server-side compilation you ought to have special assembly App_Licenses.dll in the Bin directory of your site. To create this assembly execute Build Runtime Licenses command in the licenses.licx file context menu in the Solution Explorer view. Required assembly will be created automatically.

Note that this is not necessary for precompiled ASP.NET applications (if nothing is compiled on server by user request). Precompiled applications are licensed as usual applications.

How to make dotConnect for PostgreSQL work with SQL Server 2008 Business Intelligence Solutions?

To do this install dotConnect for PostgreSQL on same computer where SQL Server 2008 resides.

I am having problems with the licensing in my project... What am I to do?

If any problems with licensing occurred in your project, you should use the License Information dialog to resolve them. You can access it from the Visual Studio menu: Tools | PostgreSQL | License Information.

Do end-users need a license?

No, end-users of your application do not require any license.

Connection pooling

I call PgSqlConnection.Open(), then Close(). Physical connection is still visible by server. Isn't it a bug?

No, it is not. This is Connection Pooling feature. Actual connection is not closed in order to be used later by your application. This boosts performance greatly.

I get exception "Timeout expired. The timeout period elapsed..." What to do?

The full text of the exception is "Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached." It clearly states that you have run out of connections available. To solve the problem increase Max Pool Size connection string parameter value. The default value is 100. Another way to get extra connections is to clear one or all of the pools. Or you can turn connection pooling off using Pooling connection string parameter.

How to prevent possible pooling problems?

You can clear the pool explicitly. Generally pool is cleared automatically when connections are idle or closed by the server. To force the operation call ClearPool or ClearAllPools methods. Another solution is to disable the pool at all (set Pooling=false in connection string). If this does not help, the problem is not caused by pooling.

Documentation problems

How to open documentation on dotConnect for PostgreSQL?

There are several ways to open dotConnect for PostgreSQL documentation:

  • Use appropriate shortcut in start menu, for instance, Start - Programs - Devart dotConnect for PostgreSQL - Documentation .
  • Use command in the IDE: Tools - PostgreSQL - dotConnect for PostgreSQL Help.
  • Position cursor on some class from Devart.Data.PostgreSql and press F1.

There is also same documentation in chm format. You can download it from our site at the following address:

I can't see the documentation in Visual Studio Help Collection.

Correctly installed documentation appears as separate node in combined collection of Visual Studio and Delphi. If you can't find dotConnect for PostgreSQL node there it is because you enabled topics filtering. To reveal the node set filter to "Devart Documentation", or "(unfiltered)", or "Visual C#" etc.

Another possible reason is that you installed some IDE after installation of dotConnect for PostgreSQL. In this case use aforementioned methods to reach documentation.

All topics in CHM file are blank.

This can happen due to some patches from Microsoft installed on your system. Please read this page to find possible solutions for the problem. In most cases it is enough to right-click on the CHM file, select Properties, click on the "Unblock" button and click "Apply" to show the contents.

ORM solutions

Are LINQ to SQL and Entity Framework supported?

The Professional Edition of dotConnect for PostgreSQL supports both LinqConnect (formerly called LINQ to PostgreSQL) and the latest version of ADO.NET Entity Framework.

Where do I start with Entity Framework or LinqConnect?

For your convenience there are brief tutorials that you can use to get acquainted with the technologies:

Are there any demo projects to play with?

Yes, dotConnect for PostgreSQL includes several Entity Framework and LinqConnect samples in C# and Visual Basic. The samples demonstrate how to use several entities and a relationship between them. You can also download separate Entity Framework Query Samples package, which is a standard Microsoft demo with added PostgreSQL connectivity.


I get concurrency error when modifying records using PgSqlDataAdapter or PgSqlDataTable. What can be wrong?

This can happen when PgSqlCommandBuilder generates a query without primary key field. To avoid it use custom update command instead of generated by PgSqlCommandBuilder. This problem should not take place if primary key field participates in SELECT statement.

No components can be found in the toolbox.

This can happen if the installation encountered some problems. You can add the components to toolbox manually. This procedure is described in the Installation article in the documentation. Note that Microsoft Web Developer 2008 Express edition does not allow working with toolbox at all.

dotConnect for PostgreSQL components in Visual Studio 2008 are grey...

Make sure you're in Component Designer view. Do not confuse with Designer view. To switch between views use context menu of .aspx file in Solution Explorer. This relates to Web projects only.

SQL Server Integration Service (SSIS) can't get the list of tables in my PostgreSQL server.

This is an architecture limitation from Microsoft, SSIS understands metadata of SQL Server only. To circumvent this you have to write queries manually.

Can I use dotConnect for PostgreSQL assemblies in the x64 process?

dotConnect for PostgreSQL assemblies are built with the /platform:anycpu option. So, you can use provider's assemblies on any platform (x86 or x64). For more information, refer to

General issues related to PostgreSQL server

Cannot connect to server on %host name%...

This is actual for mobile edition. Use IP of the server instead of DNS name. It is recommended to use internal IP address. For information on how to address target machine refer to network administrator.

How to get result set from a stored procedure?

Set PgSqlCommand.CommandType to StoredProcedure and CommandText to name of the procedure, then issue PgSqlCommand.ExecuteReader() method.
You can also do it through parameter with Direction set to System.Data.ParameterDirection.ReturnValue. For example on how to do it refer to article "Using Parameters" in dotConnect for PostgreSQL documentation.

What about performance?

We regularly carry out performance tests on different databases with miscellaneous environments. The tests show that dotConnect for PostgreSQL is much better than ODBC, OLEDB, and Npgsql. Besides that dotConnect for PostgreSQL has much more features than any other data provider.

Non-latin characters in my data are not retrieved correctly.

Use UTF-8 encoding. To enable it, set Connection.Unicode property to true or include Unicode=true; in connection string. Keep in mind, however, that this affects performance.

Mobile edition

I'm getting "A socket operation encountered a dead network" when trying to connect with Mobile Edition in run time.

Make sure that you have synchronized your device with a workstation because some synchronization tool (e.g., Microsoft ActiveSync or Windows Mobile Device Center) should be used when you work with mobile device or emulator. Before deployment make Connect and Cradle to the emulator you want to use via Device Emulator Manager (the Tools menu in Visual Studio). After cradle the ActiveSync icon in the tray should become green (indication that synchronization is successful). In the case of Windows Mobile Device Center, its Sync Center should return the "Connected" and "Sync completed" statuses.

When deploying application compiled with a trial version to mobile device, I'm getting the "trial period expired" exception. What's wrong?

The possible reason may be that the system date/time of the device is not synchronised with the date/time on your workstation; hence, the problem can be resolved by setting the date/time identical to the one on the workstation.