No constructor with a connection string in Entity Framework datacontext

Question

I am using Entity Framework 5.0 for my project. I looked on the internet and I saw that for the entity framework data context there was another constructor that had a string parameter for the connection string.

On my generated data context I don't have such a constructor. I looked into the base DbContext and it has such a constructor.

Was the code generated wrong? I generated the code from a database. Could this be the cause?

Turns out that I can edit the code generation template file to add the new constructor. Now I have added the new constructor. The file is a MyDataContext.tt file under your edmx model. There you have c# code mixed with template code. You can copy the no argument constructor from there and paste it bellow. Then you can change it and add a string argument to it and pass that argument to the DbContext constructor like this : base(myString).

Can you post the codes to make the difference more clear ..? — Bhushan Firake
– Bhushan Firake, Commented Jan 6, 2013 at 12:31
Also, DbContext is "Code-First". If you have an existing database, the typical usage is "Database-First". — Paul Fleming
– Paul Fleming, Commented Jan 6, 2013 at 12:35
@flem With EF5 even database first generates the dbcontext classes for you. It uses T4 files — scartag
– scartag, Commented Jan 6, 2013 at 12:38
@scartag. I thought db-first used ObjectContext? Did it change in EF5? — Paul Fleming
– Paul Fleming, Commented Jan 6, 2013 at 12:40

scartag · Accepted Answer · 2013-01-06 12:36:58Z

23

You can add one as needed.

Check the generated file and add an overloaded constructor.

public YourContext(string connectionStr)
        : base(connectionStr)
    {


    }

Probably better to define this in a partial class though, as every generation will require you to manually add it each time.

answered Jan 6, 2013 at 12:36

scartag

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5 Comments

Alecu Over a year ago

I believe I can also edit the .tt file but I don't know if this file is a autogenerated too.

Alecu Over a year ago

tested and changed the .tt file adding a new constructor in it. works now

sthiers Over a year ago

@Alecu: I had the same problem and did the same thing: good to know!

Alex KeySmith Over a year ago

I agree with scartag it is better to define it in a partial class, as every-time your code is generated you will loose your customisations. And it's easier to do that than edit the tt files.

Pittsburgh DBA Over a year ago

NOTE: In order to set the ConnectionString programatically, make sure you don't format it like the one in web.config or app.config. That one will contain " which needs to be changed to single quotes, or you will get a most unhelpful error message. stackoverflow.com/questions/6997035/… . Either that, or use the EntityConnectionStringBuilder.

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