An updated version of this tutorial is available here using the latest version of Visual Studio. The new tutorial uses ASP. This tutorial teaches ASP. Razor Pages is a new alternative in ASP. NET Core 2. The Razor Pages tutorial:. This following tutorial series covers ASP. The MovieDBContext class you created handles the task of connecting to the database and mapping Movie objects to database records.
One question you might ask, though, is how to specify which database it will connect to. You don't actually have to specify which database to use, Entity Framework will default to using LocalDB. In this section we'll explicitly add a connection string in the Web. SQL Server Express is not recommended for use in production web applications. LocalDB in particular should not be used for production with a web application because it is not designed to work with IIS.
By default, the Entity Framework looks for a connection string named the same as the object context class MovieDBContext for this project. NET Web Applications. Open the application root Web. Not the Web. The following example shows a portion of the Web. The two connection strings are very similar.
The first connection string is named DefaultConnection and is used for the membership database to control who can access the application.
The connection string you've added specifies a LocalDB database named Movie. We won't use the membership database in this tutorial, for more information on membership, authentication and security, see my tutorial Create an ASP. The name of the connection string must match the name of the DbContext class. You don't actually need to add the MovieDBContext connection string. If you don't specify a connection string, Entity Framework will create a LocalDB database in the users directory with the fully qualified name of the DbContext class in this case MvcMovie.
You can name the database anything you like, as long as it has the. MDF suffix. For example, we could name the database MyFilms.This topic covers how Entity Framework discovers which database connection to use, and how you can change it. Typically an Entity Framework application uses a class derived from DbContext.
This derived class will call one of the constructors on the base DbContext class to control:. If you have not done any other configuration in your application, then calling the parameterless constructor on DbContext will cause DbContext to run in Code First mode with a database connection created by convention. For example:. In this example DbContext uses the namespace qualified name of your derived context class—Demo. If both are installed, SQL Express will be used.
During installation, the EntityFramework NuGet package checks which database server is available. The NuGet package will then update the configuration file by setting the default database server that Code First uses when creating a connection by convention.C# Tutorial - Change ConnectionString at Runtime with dke.woningenkichuu.pw - FoxLearn
If SQL Express is running, it will be used. No changes are made to the configuration file if it already contains a setting for the default connection factory.
If you have not done any other configuration in your application, then calling the string constructor on DbContext with the database name you want to use will cause DbContext to run in Code First mode with a database connection created by convention to the database of that name.
If the name of the connection string matches the name of your context either with or without namespace qualification then it will be found by DbContext when the parameterless constructor is used.
If the connection string name is different from the name of your context then you can tell DbContext to use this connection in Code First mode by passing the connection string name to the DbContext constructor. This form makes it explicit that you expect the connection string to be found in your config file.
An exception will be thrown if a connection string with the given name is not found. Models created with the EF Designer are different from Code First in that your model already exists and is not generated from code when the application runs. The model typically exists as an EDMX file in your project. The designer will add an EF connection string to your app. This connection string is special in that it contains information about how to find the information in your EDMX file.
The EF Designer will also generate code that tells DbContext to use this connection by passing the connection string name to the DbContext constructor. DbContext knows to load the existing model rather than using Code First to calculate it from code because the connection string is an EF connection string containing details of the model to use. The DbContext class contains other constructors and usage patterns that enable some more advanced scenarios.
Some of these are:. You may also leave feedback directly on GitHub. Skip to main content. Exit focus mode. Use Code First with connection by convention If you have not done any other configuration in your application, then calling the parameterless constructor on DbContext will cause DbContext to run in Code First mode with a database connection created by convention. For example: namespace Demo. Use Code First with connection by convention and specified database name If you have not done any other configuration in your application, then calling the string constructor on DbContext with the database name you want to use will cause DbContext to run in Code First mode with a database connection created by convention to the database of that name.NET web application scenarios.
It also includes instructions for converting connection strings between SQL Server Express and LocalDB, and explanations of some common connection string settings.
The topic contains the following sections:. The examples show the connection strings as they appear in the ConnectionStrings element of the Web. The example assumes that you are connecting to the default SQL Server instance on the server. The following example is for a SQL Server database using integrated security log on to the server using the credentials of the Windows user account.
The example specifies a named instance of SQL Server. ContextClass in this example represents the fully qualified context class name for example, namespace.
To convert one of these connection strings to LocalDB, make the following changes:. This change assumes that you installed LocalDB with the default instance name. For more information, see Data Source later in this topic. Also remove the preceding or following semicolon. Omit the semicolon ; if the connection string already ends with one. In many cases, you can use different names in the connection string to configure the same setting; for example, the following two connection strings are equivalent:.
In the following sections, the section title specifies the version of the setting name most commonly used in ASP. NET project templates.
For settings that have alternative names, those are added in parentheses. You can use ". If you omit the instance name, the default instance is assumed. For named instances of LocalDB, replace "vThese Providers requires a connection string to connect to the database.
The way the connection string is specified has changed from the previous version of the entity framework. You can read it Database connection string in Entity Framework. There are several ways by which you can provide the connection string to EF Core application. We look at some of them in detail. The connection strings were stored in web. NET Applications.
The newer ASP. You can store connection string anywhere you wish to. For this example, we will use the appsettings. The appsetting. For example, appsettings. The configuration is stored in name-value pairs. These name-value pairs into a structured hierarchy of sections. Hence each connection string is stored as a separate node under the section ConnectionStrings as shown below.
You can name whatever you want it to be. You can create DBContext and configure it by passing the connection string in several ways depending on the type of application like ASP.
Hence we also need to read the Connection String in startup class. To Read the from the configuration, we need an instance of IConfiguration object. The IConfiguration is available to be injected via Dependency injection. Or by using the GetConnectionString method as shown below.
Next, we need to register the EFContext for Dependency injection. This done in the ConfigureServices method of the startup class. The AddDBContext extension method provided by entity framework core is used to register our Context class. Finally, you can use the DBContext by injecting it in the constructor of the Controller or services etc as shown below.
I want to share same Database information across multiple entities in Silverlight. Here is an example. I want to use this connection string but note that i put multiple entities in the metadata section. Unfortunately, combining multiple entity contexts into a single named connection isn't possible.
If you want to use named connection strings from a. By convention, that name is typically the name of the context:. However, if you end up with namespace conflicts, you can use any name you want and simply pass the correct name to the context when it is generated:.
Obviously, this strategy works best if you are using either a factory or dependency injection to produce your contexts. Another option would be to produce each context's entire connection string programmatically, and then pass the whole string in to the constructor not just the name.
This way, you can use a single connection string for every context in every project on the machine. Instead of using config files you can use a configuration database with a scoped systemConfig table and add all your settings there. With such configuration table you can create rows like such:. Then from your your application dal s wrapping EF you can easily retrieve the scoped configuration.
If you are not using dal s and working in the wire directly with EF, you can make an Entity from the SystemConfig table and use the value depending on the application you are on. First try to understand how Entity Framework Connection string works then you will get idea of what is wrong. Another alternative is, you can create your own constructor for your context and pass your own connection string and you can write some if condition etc to load defaults from web.
Better thing would be to do is, leave connection strings as it is, give your application pool an identity that will have access to your database server and do not include username and password inside connection string.
To enable the same edmx to access multiple databases and database providers and vise versa I use the following technique:. You can use the same ConnectionManager for all ObjectContexts so they all read the same settings from App. Configor edit the T4 so it creates one ConnectionManager for each in its own namespaceso that each reads separate settings.
What I understand is you want same connection string with different Metadata in it. So you can use a connectionstring as given below and replace "" part. I have used your given connectionString in same sequence.
Learn more. Asked 8 years, 11 months ago. Active 4 years, 4 months ago. Viewed k times. The meta data part of the entities will be different since I didn't name the entities the same.
Can I put multiple entities in that metadata section? Neither project can connect to it. Tim B Rico Rico 1, 4 4 gold badges 15 15 silver badges 34 34 bronze badges. Please provide a code sample; How are you connecting? Is it across domains? Scherotter Apr 25 '11 at Same Machine same domain.Tag: entity-framework.
Can someone help me understand the following two approaches to pass a connection string to the DbContext? Is this an intented behaviour of the DbContext constructor? The class DBContext Class remarks have the full explanation. In short:. Certain tools do put entries in App. The online documentation you linked states exactly where the help is.
Constructs a new context instance using the given string as the name or connection string for the database to which a connection will be made.
See the class remarks for how this is used to create a connection. You can search for your models in every assembly over reflection. Iterate through the AppDomain's assemblies and search for an attribute, interface or base class, see an example below. GetMethod "Entity" ; foreach var assembly in AppDomain.
Database Connection String in Entity Framework Core
Value to CustomerId if it is not used As you saw, the problem is that your Navigational properties are from another context They are tracked by another context. These Objects are tracked by another context. Contains t. TagName ; Contains will be translated to IN statement Probably in your case the simplest way to do it is to change the current thread culture then restore it. GetValue entityObject, null?? ToString but in this case you probably need to check if prop.
GetValue entityObject, null is IFormattable This is the classic ASP. NET await deadlock. You have been calling Wait or Result somewhere. Don't do that.Entity Framework allows a number of settings to be specified from the configuration file. All of these settings can also be applied using code. Starting in EF6 we introduced code-based configurationwhich provides a central way of applying configuration from code. Prior to EF6, configuration can still be applied from code but you need to use various APIs to configure different areas.
The configuration file option allows these settings to be easily changed during deployment without updating your code. Starting with EF4.
In EF 4. Entity Framework will still recognize database initializers set using the old format, but we recommend moving to the new format where possible. The entityFramework section was automatically added to the configuration file of your project when you installed the EntityFramework NuGet package. This page provides more details on how Entity Framework determines the database to be used, including connection strings in the configuration file.
Connection strings go in the standard connectionStrings element and do not require the entityFramework section. Starting with EF6, you can specify the DbConfiguration for EF to use for code-based configuration in your application. In most cases you don't need to specify this setting as EF will automatically discover your DbConfiguration.
To set a DbConfiguration type, you specify the assembly qualified type name in the codeConfigurationType element. An assembly qualified name is the namespace qualified name, followed by a comma, then the assembly that the type resides in.
You can optionally also specify the assembly version, culture and public key token. NET provider. Starting with EF6, the EF specific parts are now managed and registered separately. Normally you won't need to register providers yourself. This will typically be done by the provider when you install it. Providers are registered by including a provider element under the providers child section of the entityFramework section. There are two required attributes for a provider entry:. As an example here is the entry created to register the default SQL Server provider when you install Entity Framework.
Starting with EF6. Interceptors allow you to run additional logic when EF performs certain operations, such as executing database queries, opening connections, etc. Interceptors are registered by including an interceptor element under the interceptors child section of the entityFramework section.
How to: Build an EntityConnection Connection String
For example, the following configuration registers the built-in DatabaseLogger interceptor that will log all database operations to the Console. Registering interceptors via the config file is especially useful when you want to add logging to an existing application to help debug an issue. DatabaseLogger supports logging to a file by supplying the file name as a constructor parameter. By default this will cause the log file to be overwritten with a new file each time the app starts.
To instead append to the log file if it already exists use something like:. For additional information on DatabaseLogger and registering interceptors, see the blog post EF 6. The configuration section allows you to specify a default connection factory that Code First should use to locate a database to use for a context. The default connection factory is only used when no connection string has been added to the configuration file for a context.