Update Database Connections (Web Forms)

• Aug 18, 2023
• 4 minutes to read

Runtime Update

You may need to update the database connections at runtime in the following situations:

• When connection strings depend on parameters determined at runtime (current user ID or location).
• When connection strings specified in the Configuration Manager (appsettings.json) should be filtered or replaced at runtime.

Resolve Connection by Name

When you create a data source with the Data Source Wizard, the Wizard creates a connection string in the application configuration file and specifies the connection name in the SqlDataSource.ConnectionName property. The saved report layout (.REPX file) contains only the connection name. When the report layout is loaded, the connection name is resolved to a connection string, and you can implement a custom resolution service (IConnectionProviderService), as described later.

Connection Serialized with Parameters

You cannot use the custom IConnectionProviderService if a serialized connection contains connection parameters. The IConnectionProviderService.LoadConnection method is not called when a report loads a layout that contains data source connections with embedded parameters.

If you have a saved report with serialized connection parameters, open the report, clear connection parameters, and save the report. The following code snippet uses the DataSourceManager to clear connection parameters:

C#

XtraReport report;
var dataSources = DataSourceManager.GetDataSources(report, true);
foreach (var dataSource in dataSources) { 
   if(dataSource is SqlDataSource sds && !String.IsNullOrEmpty(sds.ConnectionName)) {
        sds.ConnectionParameters = null;
    }
}

Another option is the SqlDataSource.ConfigureDataConnection event. Handle the ConfigureDataConnection event and use the e.ConnectionParameters property to access and modify connection parameters. You can register the WebDocumentViewerOperationLogger service and subscribe to that event in the WebDocumentViewerOperationLogger.ReportOpening method.

How to Implement a Custom Connection Resolution Service

1. Implement the IConnectionProviderFactory service:

   C#

   using DevExpress.DataAccess.Web;
   using DevExpress.DataAccess.Wizard.Services;
   // ... 
       public class MyConnectionProviderFactory : IConnectionProviderFactory
       {
           public IConnectionProviderService Create()
           {
               return new MyConnectionProviderService();
           }
       }
   

   VB.NET

   Imports DevExpress.DataAccess.Web
   Imports DevExpress.DataAccess.Wizard.Services
   ' ...
       Public Class MyConnectionProviderFactory
           Implements IConnectionProviderFactory
           Public Function Create() As IConnectionProviderService Implements IConnectionProviderFactory.Create
               Return New MyConnectionProviderService()
           End Function
       End Class
   

   The service returns an instance of the IConnectionProviderService that supplies connections.

2. Implement the IConnectionProviderService class:

   C#

   using DevExpress.DataAccess.ConnectionParameters;
   using DevExpress.DataAccess.Sql;
   using DevExpress.DataAccess.Wizard.Services;
   using System.Collections.Generic;
   // ...
       public class MyConnectionProviderService : IConnectionProviderService
       {        
           public SqlDataConnection LoadConnection(string connectionName)
           {
               switch (connectionName)
               {
                   case ("NWindConnectionString"):
                       return new SqlDataConnection("NWindConnectionString",
                               new MsSqlConnectionParameters()
                               {
                                   AuthorizationType = MsSqlAuthorizationType.Windows,
                                   DatabaseName = "Northwind",
                                   ServerName = "localhost"
                               });
                   default:
                       throw new KeyNotFoundException($"Connection string '{connectionName}' not found.");
               }
           }
       }
   

   VB.NET

   Imports DevExpress.DataAccess.ConnectionParameters
   Imports DevExpress.DataAccess.Sql
   Imports DevExpress.DataAccess.Wizard.Services
   '...
       Public Class MyConnectionProviderService
           Implements IConnectionProviderService
   
           Public Function LoadConnection(ByVal connectionName As String) As SqlDataConnection Implements IConnectionProviderService.LoadConnection
               Select Case connectionName
                   Case ("NWindConnectionString")
                       Return New SqlDataConnection("NWindConnectionString", New MsSqlConnectionParameters() With {.AuthorizationType = MsSqlAuthorizationType.Windows, .DatabaseName = "Northwind", .ServerName = "localhost"})
                   Case Else
                       Throw New KeyNotFoundException($"Connection string '{connectionName}' not found.")
               End Select
           End Function
       End Class
   

   When the Document Viewer or Report Designer Preview loads a report, it calls the IConnectionProviderService.LoadConnection method and allows you to return a connection with the specified name stored in a report.

   You can use various DataConnectionParametersBase descendants to establish a connection to different DBMS and data files in different formats, such as:

   • MS SQL Server - MsSqlConnectionParameters
   • Oracle - OracleConnectionParameters
   • XML file - XmlFileConnectionParameters.

   To specify a custom connection string, use the CustomStringConnectionParameters instance.

   For more information, review the following articles:

   • Data Sources
   • SqlDataSource - Best Practices for Managing Connection Settings in XtraReports

How to Register a Service

Register the MyConnectionProviderFactory service at application start:

C#

protected void Application_Start() {
    // ...
    DevExpress.XtraReports.Web.WebDocumentViewer.DefaultWebDocumentViewerContainer.RegisterConnectionProviderFactory<MyConnectionProviderFactory>();
    /...
}

VB.NET

Protected Sub Application_Start()
    ' ...
        DevExpress.XtraReports.Web.WebDocumentViewer.DefaultWebDocumentViewerContainer.RegisterConnectionProviderFactory(Of MyConnectionProviderFactory)()
    ' ...
End Sub

Tip

If you use a custom report storage, you can update a connection in the ReportStorageWebExtension.GetData method when the report layout is loaded. Review the following help topic for more information on the report storage: Add a Report Storage (ASP.NET Web Forms).