Entity framework code first migration to multiple database
code-first ef-code-first ef-migrations entity-framework entity-framework-6
Question
Lets say we have the architecture model of web application where we have 1 database per 1 account. Database structure is the same for these accounts and differs only on data with in. How can i configurate a migrations in code first model.
Accepted Answer
Now I have next solution. In the main method or in global.asax something like this:
var migration_config = new Configuration();
migration_config.TargetDatabase = new DbConnectionInfo("BlogContext");
var migrator = new DbMigrator(migration_config);
migrator.Update();
migration_config.TargetDatabase = new DbConnectionInfo("BlogContextCopy");
migrator = new DbMigrator(migration_config);
migrator.Update();
Connection strings for example in app_config file:
<connectionStrings>
<add name="BlogContext" providerName="System.Data.SqlClient" connectionString="Server=(localdb)\v11.0;Database=MigrationsDemo.BlogContext;Integrated Security=True;"/>
<add name="BlogContextCopy" providerName="System.Data.SqlClient" connectionString="Server=(localdb)\v11.0;Database=MigrationsDemo.BlogContextCopy;Integrated Security=True;"/>
</connectionStrings>
Configuration class and context:
internal sealed class Configuration : DbMigrationsConfiguration<MigrationsDemo.BlogContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = true;
AutomaticMigrationDataLossAllowed = true;
}
protected override void Seed(MigrationsDemo.BlogContext context) {
}
}
public class BlogContext : DbContext {
public BlogContext() {}
public BlogContext(string connection_name) : base(connection_name) {
}
public DbSet<Blog> Blogs { get; set; }
}
Popular Answer
In addition to your excellent answer, you can use an external config file (i.e. "clients.json") instead of hardcoding them, put all the database infos in key-value pairs into the json file and load it during startup.
Then, by iterating over the key-value pairs, you can do the initialization.
The clients.json:
{
"DatabaseA": "DatabaseAConnectionString",
"DatabaseB": "DatabaseBConnectionString",
"DatabaseC": "DatabaseCConnectionString",
...
}
Provide a method to handle the migrations:
public static void MigrateDatabases(IDictionary<string,string> databaseConfigs)
{
foreach (var db in databaseConfigs)
{
var config = new Configuration
{
TargetDatabase = new DbConnectionInfo(db.Value, "System.Data.SqlClient")
};
var migrator = new DbMigrator(config);
migrator.Update();
}
}
Then during startup, (I use OWIN, so it's in my Startup.cs, could also be global.asax.cs):
string json;
var path = HttpRuntime.AppDomainAppPath;
using (var reader = new StreamReader(path + @"Config\clients.json"))
{
json = reader.ReadToEnd();
}
var databases = JsonConvert.DeserializeObject<IDictionary<string, string>>(json);
MigrateDatabases(databases);
Works like a charm for me :)
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