Change Connection String at Runtime in EF 6

Question

I mostly use my dbcontext with using statements like this:

using (var context = new MyContext())
{
}

But I later had to add a project with a function to change the database. I found out that I could change my dbcontext constructor to this:

public MyContext(string connectionstring)
        : base(connectionstring)
{
}

I made a class with a property for the connectionstring:

public static class DbAccessor
{
    public static string ConnectionStringForContext { get; set; }
}

I set this property in the beginning and my using statements look like this:

using (var context = new MyContext(DbAccessor.ConnectionStringForContext) 
{}

It works, but my connection string is now everywhere and I feel like I should not do that with connection strings. Is there a better way of doing this? What would be the best way to handle my Connection Strings if I want to change them? Should I stop using these using statements?

I've seen this question: Entity Framework change connection at runtime

But the difference is, that I have a functioning solution, but I don't want to have my connection string everywhere. If I used that extension method inside every using statement. It would almost be like my solution just one line more in every using statement...

Possible duplicate of [Entity Framework change connection at runtime](http://stackoverflow.com/questions/20216147/entity-framework-change-connection-at-runtime) — Nick De Beer, Feb 04 '16 at 10:33

score 3 · Accepted Answer · answered Feb 04 '16 at 10:25

You could try a static factory method (or factory class whichever you prefer) on your context which uses the connection string like so:

public class MyContext : ...
{
    public MyContext(string connectionstring)
        : base(connectionstring)
    {
    }

    public static MyContext Create()
    {
        return new MyContext(DbAccessor.ConnectionStringForContext);
    }
}

and then you can create your context like so:

using (var context = MyContext.Create())
{
}

Thanks! Now I just have to do it once. That's what I wanted :D — A.Ima, Feb 04 '16 at 12:12

David McLean · Answer 2 · 2016-02-04T10:50:56.387

If I have understood you correctly you need to be able to support your application connecting to more than one database. You can do this pretty much as you are but have say two properties on your DBAccessor class, remove the set and get the relevant connection from your config, that way your config is always maintained in the application config.

public static class DbAccessor
{
    public static string ConnectionStringForDBOne { get { return ConfigurationManager.ConnectionStrings["DBOne"].ConnectionString} }
    public static string ConnectionStringForDBTwo { get { return ConfigurationManager.ConnectionStrings["DBTwo"].ConnectionString} }
}

Then add some static creators to make life easier:

public MyContext(string connectionstring)
        : base(connectionstring)
{
    public static MyContext CreateContextDBOne()
    {
        return new MyContext(DbAccessor.ConnectionStringForDBOne);
    }

    public static MyContext CreateContextDBTwo()
    {
        return new MyContext(DbAccessor.ConnectionStringForDBTwo);
    }
}

Then use them in code:

using (var context = MyContext.CreateContextDBOne())
{
}

using (var context = MyContext.CreateContextDBTwo())
{
}

score 0 · Answer 3 · edited May 23 '17 at 12:18

0

You have one place for connection string, it's ok. If you want change connection string you change only DbAccessor.ConnectionStringForContext, it's good. Or if you don't want param in contructor you can try solution from this question.

edited May 23 '17 at 12:18

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answered Feb 04 '16 at 10:25

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Change Connection String at Runtime in EF 6

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