how to generate barcode c# code Changing an Independent Association into a Foreign Key Association in Font

Drawing QR Code ISO/IEC18004 in Font Changing an Independent Association into a Foreign Key Association

6-16. Changing an Independent Association into a Foreign Key Association
Quick Response Code Creator In None
Using Barcode drawer for Font Control to generate, create Quick Response Code image in Font applications.
www.OnBarcode.com
Drawing Data Matrix In None
Using Barcode creator for Font Control to generate, create ECC200 image in Font applications.
www.OnBarcode.com
Problem
EAN13 Drawer In None
Using Barcode generator for Font Control to generate, create EAN-13 image in Font applications.
www.OnBarcode.com
PDF-417 2d Barcode Maker In None
Using Barcode generation for Font Control to generate, create PDF 417 image in Font applications.
www.OnBarcode.com
You have a model that uses an independent association and you want to change it to a foreign key association.
Generating Barcode In None
Using Barcode maker for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
UCC.EAN - 128 Maker In None
Using Barcode creator for Font Control to generate, create EAN / UCC - 13 image in Font applications.
www.OnBarcode.com
BEYOND THE BASICS WITH MODELING AND INHERITANCE
Code-128 Creation In None
Using Barcode generator for Font Control to generate, create Code128 image in Font applications.
www.OnBarcode.com
Painting MSI Plessey In None
Using Barcode generator for Font Control to generate, create MSI Plessey image in Font applications.
www.OnBarcode.com
Solution
QR Code Drawer In Visual Studio .NET
Using Barcode drawer for .NET Control to generate, create Quick Response Code image in Visual Studio .NET applications.
www.OnBarcode.com
Denso QR Bar Code Generation In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create QR Code 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Let s say you have a model like the one shown in Figure 6-40.
Creating UCC.EAN - 128 In Java
Using Barcode generation for Java Control to generate, create EAN / UCC - 14 image in Java applications.
www.OnBarcode.com
Barcode Maker In None
Using Barcode creator for Online Control to generate, create Barcode image in Online applications.
www.OnBarcode.com
Figure 6-40. A model for vehicles and tickets using an independent association To change the association from an independent association to a foreign key association, do the following: 1. 2. 3. Right-click the Ticket entity and select Add property LicenseNumber. Scalar Property. Rename the
1D Creation In Java
Using Barcode encoder for Java Control to generate, create Linear image in Java applications.
www.OnBarcode.com
QR-Code Decoder In .NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
View the Mapping Details window for the association. Remove the mapping to the Ticket table by selecting <Delete> from the Maps to Ticket control. Right-click the association and view the properties. Click in the button in the Referential Constraint control. In the dialog box select the Vehicle entity in the Principal dropdown control. The Principal Key and the Dependent Property should both be set to LicenseNumber as shown in Figure 6-41. View the Mapping Details window for the Ticket entity. Map the LicenseNumber column to the LicenseNumber property as shown in Figure 6-42.
Matrix Barcode Creator In Java
Using Barcode generator for Java Control to generate, create 2D Barcode image in Java applications.
www.OnBarcode.com
Code-128 Scanner In C#
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
The final model is shown in Figure 6-43.
Painting PDF-417 2d Barcode In Visual Studio .NET
Using Barcode drawer for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Paint PDF-417 2d Barcode In None
Using Barcode printer for Online Control to generate, create PDF 417 image in Online applications.
www.OnBarcode.com
Figure 6-41. Creating the referential constraint for the foreign key association
Code 39 Full ASCII Scanner In VB.NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
GTIN - 13 Drawer In Visual Studio .NET
Using Barcode encoder for ASP.NET Control to generate, create EAN13 image in ASP.NET applications.
www.OnBarcode.com
BEYOND THE BASICS WITH MODELING AND INHERITANCE
Figure 6-42. Mapping the LicenseNumber column to the LicenseNumber property for the Ticket entity
Figure 6-43. The model with the independent association changed to a foreign key association
How It Works
When you change an independent association into a foreign key association, most of your existing code will continue to work. You will find it easier now to associate two entities by simply setting the exposed foreign key to the appropriate value. To change a relationship with an independent association, you need to create a new instance of EntityKey and set the entity s xxxReference.EntityKey to this new instance. With a foreign key association, you simply set the exposed foreign key property to the key value. Foreign key associations are not currently supported for many-to-many associations because these associations must be mapped to the underlying link table. A future version of Entity Framework may support foreign key associations along with payloads for many-to-many associations.
Working with Object Services
This chapter contains a rather eclectic collection of recipes that provide practical solutions to common problems in real-world applications. We build our applications to tolerate changes in deployment environments and make our applications flexible enough so that few if any configuration details need to be hard-coded. The first three recipes provide you with tools to meet these challenges. The remaining recipes cover topics such as Entity Framework s Pluralization Service, using the edmgen.exe utility, working with identifying relationships, and retrieving objects from an object context.
7-1. Dynamically Building a Connection String
Problem
You want to dynamically build the connection string for your application.
Solution
Many real-world applications start out on a developer s desktop; move through one or more testing, integration, and staging environments; and finally end up in a production deployment. You want to dynamically configure the application s connection string depending on the current environment. To dynamically build the connection string for your application, follow the pattern in Listing 7-1. Listing 7-1. Dynamically building a connection string public static class ConnectionStringManager { public static string EFConnection = GetConnection(); private static string GetConnection() { var sqlBuilder = new SqlConnectionStringBuilder(); // figure out the environment // strings here should come from a config file string myHost = Dns.GetHostName(); if (myHost.ToLower().Contains("test")) sqlBuilder.DataSource = @"TestSql01"; else if (myHost.ToLower().Contains("staging"))
WORKING WITH OBJECT SERVICES
sqlBuilder.DataSource = @"StagingSql01"; else if (myHost.ToLower().Contains("prod")) sqlBuilder.DataSource = @"ProdSql01"; else sqlBuilder.DataSource = @"localhost"; // fill in the rest sqlBuilder.InitialCatalog = "EFRecipes"; sqlBuilder.IntegratedSecurity = true; sqlBuilder.MultipleActiveResultSets = true; var eBuilder = new EntityConnectionStringBuilder(); eBuilder.Provider = "System.Data.SqlClient"; eBuilder.Metadata = "res://*/Recipe1.csdl|res://*/Recipe1.ssdl|res://*/Recipe1.msl"; eBuilder.ProviderConnectionString = sqlBuilder.ToString(); return eBuilder.ToString(); } } public partial class EFRecipesEntities { partial void OnContextCreated() { this.Connection.ConnectionString = ConnectionStringManager.EFConnection; } }
How It Works
When you add an ADO.NET Entity Data Model to your project, Entity Framework adds an entry to the <connectionStrings> section in your project s .config file. At runtime, the constructor for the object context is passed the key for this configuration entry (EFRecipesEntities for the recipes in this book). Given this key, the object context uses the connection string found in the .config file. To dynamically create the connection string based on the environment in which our application is deployed, we created the ConnectionStringManager class (refer to Listing 7-1). In the GetConnection() method, we check the name of the machine the application is on and use it to determine the target database server. To keep things simple, we hard-coded the names of machines here (you would probably want to put them in a .config file). To use our ConnectionStringManager, we implemented the OnContextCreated() partial method inside EFRecipesEntities partial class. In our implementation of the OnContextCreated() partial method, we get the statically built connection string from the ConnectionStringManager. The object context will use this connection string to connect to our database server. You don t need to change anything else in your application. Each time you get a new instance of your object context, the OnContextCreated() method will get the connection string created when the static ConnectionStringManager class was created.
Copyright © OnBarcode.com . All rights reserved.