Modify And Save an EF EntityDataSource Bound Entity From Code Behind

If you're using databound controls (e.g. FormView) and binding them to an EntityDataSource you might want to be able to modify (and save) the underlying entity from code. For example, if you have a Question entity bound to a FormView via an EntityDataSource you might want a button to allow the use to vote up or down the question (like StackOverflow for example). To be able to do this without extra trips to the database, the first thing we need to do is get hold of the EF ObjectContext that the EntityDataSource is using.

        // Context that we can use for code-behind operations
        ObjectContext questionObjectContext = null;


        protected void QuestionEntityDataSource_ContextCreated(object sender, EntityDataSourceContextCreatedEventArgs e)
        {
            questionObjectContext = e.Context;
        }

When the QuestionEntityDataSource creates it's context, we take a reference to it in our private field questionObjectContext.

Now in the button click we can up-vote the question:

 

        protected void btnVoteUp_Click(object sender, EventArgs e)
        {
            // force a databind to ensure we have a DataItem in the FormView        
            FormView1.DataBind();

            // Get the actual entity represented by the FormView
            Question questionToUpdate = FormView1.DataItem.WrappedEntity<Question>();

            // Vote-up
            questionToUpdate.VoteScore++;
           
            // using our 'copy' of the EntityDataSource ObjectContext, save the changes
            questionObjectContext.SaveChanges(true);
           
            // Force rebind of FormView to ensure newest data displayed
            FormView1.DataBind();                     
        }

This method feels like a bit of a hack, but ideally you would provide a client-side AJAX version, only if JavaScript is disabled on the client do we use this server-side up-vote.

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