Question

I have a system that supports multiple products. Each product has its own database with the same exact schema.

When I pass in the connection string as a parameter to my Data Context constructor it always uses the default database listed in the connection string, or the default database of the user connecting if I do not provide an Initial Catalog in the connection string.

I would like to be able to have the system utilize a database without having to change the connection string and by passing in the database name as a parameter.

Here is an example of the code I am using:

class Program     {         static void Main(string[] args)         {             var d = new Data('Data Source=(LOCAL);Initial Catalog=Database1;Integrated Security=true;');              var d1 = new Data('Data Source=(LOCAL);Initial Catalog=Database2;Integrated Security=true;');              Console.ReadLine();         }     }      internal class Data     {         public Data(string connection)         {              using (var ctx = new DataClassDataContext(connection))             {                 var query = from c in ctx.MyTable select c;                 try                 {                     Console.WriteLine(query.Count());                 }                 catch (Exception ex)                 {                     Console.WriteLine(ex.Message);                 }                }         }     } 

If this code gets executed, then the first result will pull from Database1 and the second result will pull from Database2. I would like it to have the ability to pull from a database that is not provided in the connection string. The reason for this is because the database could change based on a specific scenario but the connection string will remain the same.

Here is an example of what I am using to ‘fake’ it, but I don’t really think this is the best solution for this:

class oConnection     {         public string Server { get; set; }         public string Database { get; set; }         public bool IntegratedSecurity { get; set; }         public string UserName { get; set; }         public string Password { get; set; }     }      class Program     {         static void Main(string[] args)         {             var d = new Data(new oConnection                                  {                                      Database = 'Database1',                                      Server = '(Local)',                                      IntegratedSecurity = true                                  });              var d1 = new Data(new oConnection                                   {                                       Database = 'Database2',                                       Server = '(Local)',                                       IntegratedSecurity = true                                   });             Console.ReadLine();         }     }      internal class Data     {         private static string BuildConnection(oConnection connection)         {             var sb = new StringBuilder();             sb.Append('Data Source=' + connection.Server + ';Initial Catalog=' + connection.Database + ';');             if(connection.IntegratedSecurity)             {                 sb.Append('Integrated Security=true;');             }             else             {                 sb.Append('user id=' + connection.UserName + ';password=' + connection.Password);             }             return sb.ToString();         }          public Data(oConnection connection)         {              using (var ctx = new DataClassDataContext(BuildConnection(connection)))             {                 var query = from c in ctx.MyTable select c;                 try                 {                     Console.WriteLine(query.Count());                 }                 catch (Exception ex)                 {                     Console.WriteLine(ex.Message);                 }             }         }     } 

Another note: the goal of this is really to be able to support not having multiple different connection strings when running queries that will span across multiple databases. For example: If I want to query the account records from a database and then query some sort of lookup data from another database, I would have to create a new connection string for the context.

Any help would be appreciated. Thanks

Answer 1

Use the constructor that receives System.Data.IDbConnection connection. You can use the same connection string, and call connection.ChangeDatabase(‘mydb’) before passing it to the constructor. Alternatively you can add a new constructor on the partial class, so the calling call doesn’t has to deal with that.