Question

In my controller, I always end up with something like:

[HttpPost]
public ActionResult General(GeneralSettingsInfo model)
{
    try
    {
        if (ModelState.IsValid)
        {
            // Upload database
            db.UpdateSettingsGeneral(model, currentUser.UserId);
            this.GlobalErrorMessage.Type = ErrorMessageToViewType.success;
        }
        else
        {
            this.GlobalErrorMessage.Type = ErrorMessageToViewType.alert;
            this.GlobalErrorMessage.Message = "Invalid data, please try again.";
        }
    }
    catch (Exception ex)
    {
        if (ex.InnerException != null)
            while (ex.InnerException != null)
                ex = ex.InnerException;

        this.GlobalErrorMessage.Type = ErrorMessageToViewType.error;
        this.GlobalErrorMessage.Message = this.ParseExceptionMessage(ex.Message);
    }

    this.GlobalErrorMessage.ShowInView = true;
    TempData["Post-data"] = this.GlobalErrorMessage;

    return RedirectToAction("General");
}

and what I would like to do would something like:

[HttpPost]
public ActionResult General(GeneralSettingsInfo model)
{
    saveModelIntoDatabase(
        ModelState, 
        db.UpdateSettingsGeneral(model, currentUser.UserId)
    );

    return RedirectToAction("General");
}

How would I pass a function as a parameter? Just like we do in javascript:

saveModelIntoDatabase(ModelState, function() {
    db.UpdateSettingsGeneral(model, currentUser.UserId)
});

Answer 1

It sounds like you want a delegate. It’s not immediately obvious to me what your delegate type should be here – possibly just Action:

SaveModelIntoDatabase(ModelState, 
    () => db.UpdateSettingsGeneral(model, currentUser.UserId));

Where SaveModelIntoDatabase would be:

public void SaveModelIntoDatabase(ModelState state, Action action)
{
    // Do stuff...

    // Call the action
    action();
}

If you want the function to return something, use a Func; if you need extra parameters, just add them as type parameters – there’s Action, Action<T>, Action<T1, T2> etc.

If you’re new to delegates, I’d strongly suggest getting much more familiar with them before going much further in C# – they’re really handy, and an essential part of modern idiomatic C#. There’s a lot on the web about them, including:

• MSDN delegates introduction (linking to other articles)
• My article on delegates and events