Single Row Table in Entity Framework 6
I couldn't find a solution to this problem, but the title clearly shows what I want.
Is it possible to create a table with one row (I only need to store a boolean in the table)? And how can I customize this constraint using the Fluent API?
you can make one of the columns the primary and also only allow one value. Unfortunately the current version of the api currently supports the default
public class StatusIdentifer
{
[DefaultValue("1")]
[Key]
public int id {get; set}; //set can be removed here?
public bool status {get:set;} //your boolean value
}
the trick is not to expose any set methods for id.
at the database level, you can still break the paradigm. The answer here talks about how to create a check constraint
public void InitializeDatabase(MyRepository context) {
if (!context.Database.Exists() || !context.Database.ModelMatchesDatabase()) {
context.Database.DeleteIfExists();
context.Database.Create();
context.ObjectContext.ExecuteStoreCommand("CREATE UNIQUE CONSTRAINT...");
context.ObjectContext.ExecuteStoreCommand("CREATE INDEX...");
context.ObjectContext.ExecuteStoreCommand("ETC...");
}
}
With a bit of research, I came up with this solution. I created an initializer for the database (because ExecuteSqlCommand cannot be called in the OnModelCreating method).
class UserDbInitializer : CreateDatabaseIfNotExists<UserDbContext>
{
protected override void Seed(UserDbContext context)
{
context.Database.ExecuteSqlCommand(
"CREATE TABLE __Lock(" +
"Id char(1) NOT NULL DEFAULT 'X'," +
"Lock bit NOT NULL," +
"CONSTRAINT PK_LOCK PRIMARY KEY (Id)," +
"CONSTRAINT CK_LOCK_Locked CHECK (Id='X'))"
);
context.Database.ExecuteSqlCommand(
"INSERT INTO __Lock VALUES('X', 0)"
);
base.Seed(context);
}
}
And in UserDbContext the following property:
public bool Locked
{
get
{
return Database.SqlQuery<bool>("SELECT Lock FROM __Lock").SingleAsync().Result;
}
set
{
if (value)
Database.ExecuteSqlCommand("UPDATE __Lock SET Lock = 1");
else
Database.ExecuteSqlCommand("UPDATE __Lock SET Lock = 0");
}
}
Hope this helps others :)