CON-1339 - Support for SQL Based Session State

It appears that any out-of-process session mode would have this bug, not just SQLServer. For example, Redis.

I've very keen to see this one fixed, as it prevents Umbraco Forms from using an out of process session state on load balanced websites.

We have a workaround - we have set individual web servers to use in-process session state and used "sticky sessions" to ensure repeat requests are sent to the same web server. However this isn’t ideal and prevents us from reaping the full benefits of a multi-server load balanced environment along with introducing the possibility of session state data loss due to servers being taken out of load.

Just an update on this issue, this is something we will need to schedule in for the new year (due to limited time left of this year)

This is a large t-shirt sized task and will take a large amount of a sprint to go through & update the Forms codebase as needed to get it to work with a SQL Session state or Redis

PR for this is here - https://github.com/umbraco/Forms/pull/175

At first I was unable to test & reproduce this when using a SQL based SessionState, only when I put TextField and other FieldTypes from the Umbraco.Forms.Provider class directly into a Session & tried to retrieve it again.

== Test Notes ==

• To confirm the issue in a simple template/view have the following code - which will throw a YSOD about serialization

@{
    var field = new Umbraco.Forms.Core.Providers.FieldTypes.Textarea();
    field.Name = "My Field";

    Session["myField"] = field;
}

@{
    var myField = Session["myField"] as Umbraco.Forms.Core.Providers.FieldTypes.Textarea;
    var fieldName = myField.Name;
}

Apply the PR to your codebase & re-run the page with the above code in it's view & ensure no YSOD is thrown

OK updated a few more classes where some were marked as [Serializable] - hopefully should have them all now. Let me know if you think I may have missed anything obvious @Shandem

tested and looks good!

That's awesome news! Any estimation on when it will be available here?: https://our.umbraco.org/projects/developer-tools/umbraco-forms/