This sample project demonstrates how to use a custom data adapter. 
First, add a custom data adapter:
...
	// Clearing standard data adapters, if necessary
	StiOptions.Services.Databases.Clear();
	// Adding a Custom PostgreSQL data adapter
	StiOptions.Services.Databases.Add(new CustomPostgreSQLDatabase());
	StiOptions.Services.DataAdapters.Add(new CustomPostgreSQLAdapterService());
...
Finally, add a connection to the report:
...
	var report = new StiReport();
	// Adding a connection to the report from code
	var database = new CustomPostgreSQLDatabase("CustomData1", "Server=127.0.0.1; Port=5432; Database=myDataBase; User Id=myUsername; Password=myPassword;");
	report.Dictionary.Databases.Add(database);
	report.DesignV2WithWpf();
...
In the screenshot below you can see the result of the sample code: