I'm build my webapi project based on this article: A simple POC using ASP.NET Web API, Entity Framework, Autofac, Cross Domain Support
However, I need to pass a connection string to the DbContext
because a user that connects to the webapi can select a different database to work with.
Where and what is that best way to implement this? In the controller, having a separate 'service' or a singleton?
One way would be to have multiple ConnectionStrings in your web config. You could then select which ConnectionString to use depending on a parameter passed to your webapi:
In your web config:
<connectionStrings>
<add name="dataBase1" connectionString="/*db info here*/" providerName="System.Data.SqlClient" />
<add name="dataBase2" connectionString="/*db info here*/" providerName="System.Data.SqlClient" />
</connectionStrings>
Then in your code:
public someobject GetData(/*arguments*/, string dbType)
{
var connectionString = dbType == 'dataBase1'
? ConfigurationManager.ConnectionString['dataBase1'].toString()
: ConfigurationManager.ConnectionString['dataBase2'].toString()
/*then pass connectionString to dbContext*/
var dbContext = new DbContext(connectionString);
}
I'm currently building a website that requires multiple databases also. This is the basics (for now). It may not be the best/efficient way, but it does the job so that I can continue working on the site.
Let's say you have this connection and everything there is correct, except the database name can change.
<add name="MyDbContext" connectionString="Server=SomeConnection;Database=SomeDatabase;"providerName="System.Data.SqlClient" />
You can create a connection string on the fly with this
public MyDbContext CreateDbContext(string databaseName)
{
SqlConnectionStringBuilder sqlBuilder = new SqlConnectionStringBuilder(System.Configuration.ConfigurationManager.ConnectionStrings["MyDbContext"].ConnectionString); // Gets the default connection
sqlBuilder.InitialCatalog = databaseName; // Update the database name
return new MyDbContext(sqlBuilder.ToString());
}
Also, unless you want to automatically create a database if it doesn't exist, possibly from incorrect database name, you need to set the initializer. Simply pass the initializer null to prevent ef from automatically creating one. I set this in the constructor of MyDbContext
public class MyDbContext : DbContext
{
/* some other constructors */
public MyDbContext(string nameOrConnectionString, bool createDb)
: base(nameOrConnectionString)
{
if(!createdDb)
{
System.Data.Entity.Database.SetInitializer<MyDbContext>(null);
}
}
}
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