Pass connection string to code-first DbContext

Question

How do I pass a connection string to entity framework s code-first DbContext  My database generation works correctly when both DbContext and the connection string in web config is in the same project and named the same way  But now I need to move the DbContext to another project so I m testing passing a connection string to it as follows   Model  amp  Context  public class Dinner       public int DinnerId   get  set        public string Title   get  set       public class NerdDinners   DbContext       public NerdDinners string connString            base connString                  public DbSet lt Dinner gt  Dinners   get  set        Action      public ActionResult Index                 var db   new NerdDinners ConfigurationManager ConnectionStrings  NerdDinnerDb   ConnectionString            var dinners    from d in db Dinners                       select d  ToList            return View dinners           Web Config   lt connectionStrings gt     lt add name  NerdDinnerDb  connectionString  Data Source  DataDirectory NerdDinners sdf  providerName  System Data SqlServerCe 4 0   gt       lt  connectionStrings gt    If I set a breakpoint in the action an analyze the db  the connection string is there  but it does not create or find the database or anything      A network-related or instance-specific error occurred while establishing a connection to SQL Server  The server was not found or was not accessible  Verify that the instance name is correct and that SQL Server is configured to allow remote connections   provider  Named Pipes Provider  error  40 - Could not open a connection to SQL Server

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In your DbContext  create a default constructor for your DbContext and inherit the base like this       public myDbContext             base  MyConnectionString       connectionstring name define in your web config

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When using an EF model  I have a connection string in each project that consumes the EF model  For example  I have an EF EDMX model in a separate class library  I have one connection string in my web  mvc  project so that it can access the EF db    I also have another unit test project for testing the repositories  In order for the repositories to access the EF db  the test project s app config file has the same connection string    DB connections should be configured  not coded  IMO

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Can t see anything wrong with your code  I use SqlExpress and it works fine when I use a connection string in the constructor    You have created an App Data folder in your project  haven t you

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I have a little solution example for that problem   MyDBContext cs   public MyDBContext DBConnectionType ConnectionType      base  ConnMain             if ConnectionType  DBConnectionType MainConnection                    this Database Connection ConnectionString   ConfigurationManager ConnectionStrings  ConnMain   ConnectionString                 else if ConnectionType  DBConnectionType BackupConnection                    this Database Connection ConnectionString   ConfigurationManager ConnectionStrings  ConnBackup   ConnectionString                 MyClass cs  public enum DBConnectionType        MainConnection 0      BackupConnection 1      frmMyForm cs   MyDBContext db   new MyDBContext DBConnectionType MainConnection                                    or   MyDBContext db   new MyDBContext DBConnectionType BackupConnection

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If you are constructing the connection string within the app then you would use your command of connString  If you are using a connection string in the web config  Then you use the  name  of that string

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A little late to the game here  but another option is   public class NerdDinners   DbContext       public NerdDinners string connString                this Database Connection ConnectionString   connString            public DbSet lt Dinner gt  Dinners   get  set

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For anyone who came here trying find out how to set connection string dinamicaly  and got trouble with the solutions above  like  Format of the initialization string does not conform to specification starting at index 0    when setting up the connection string in the constructor  This is how to fix it   public static string ConnectionString       get           if  ConfigurationManager AppSettings  DevelopmentEnvironment       true               return ConfigurationManager ConnectionStrings  LocalDb   ConnectionString          else             return ConfigurationManager ConnectionStrings  ExternalDb   ConnectionString           public ApplicationDbContext     base ConnectionString

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Check the syntax of your connection string in the web config   It should be something like ConnectionString  Data Source C  DataDictionary NerdDinner sdf

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from here    protected override void OnConfiguring DbContextOptionsBuilder optionsBuilder              optionsBuilder UseSqlServer ConfigurationManager ConnectionStrings  BloggingDatabase   ConnectionString           note you may need to add Microsoft EntityFrameworkCore SqlServer

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Thought I d add this bit for people who come looking for  How to pass a connection string to a DbContext   You can construct a connection string for your underlying datastore and pass the entire connection string to the constructor of your type derived from DbContext    Re-using Code from  Lol Coder  Model  amp  Context  public class Dinner       public int DinnerId   get  set        public string Title   get  set       public class NerdDinners   DbContext       public NerdDinners string connString            base connString                  public DbSet lt Dinner gt  Dinners   get  set        Then  say you construct a Sql Connection string using the SqlConnectioStringBuilder like so   SqlConnectionStringBuilder builder   new SqlConnectionStringBuilder GetConnectionString       Where the GetConnectionString method constructs the appropriate connection string and the SqlConnectionStringBuilder ensures the connection string is syntactically correct  you may then instantiate your db conetxt like so   var myContext   new NerdDinners builder ToString

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After reading the docs  I have to pass the name of the connection string instead   var db   new NerdDinners  NerdDinnerDb

[c#] Pass connection string to code-first DbContext

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