How can I pass variables from form to form?

Question

When working with a collection of forms that the user must step through, is it better to pass the data foward when creating a new instance of that form, or is it better to call a function from the previous form? I have some code written that calls the previous routine, and it looks ugly, and I can't quite think of a reason why it was done that way. The only reason I could come up with was if the data was large, and there was a good chance that the user wouldn't use the data except in a special case.

Answer 1

That's a subjective question for the most part. I personally took a route that seemed easier to maintain for people who will have to deal with my code later. I would instantiate the form, load the public properties with whatever I was trying to pass and then make the form visible. That way, anyone editing the 'new' form knew that all the data was pre-loaded. Anyone editing the 'old' form knew where to load any new properties.

Answer 2

If the new form will need the data immediately then it is probably better to pass it in the constructor of this form.

Answer 3

If you put all your shared data in a class, and then pass a reference to an instance of that class to the constructor on each form, then it doesn't matter how large the data is as it is only a reference being passed each time.

This has advantage that your forms are not tied to each other.

Answer 4

Use a new form and you can pass the values from form on other using server.transfer You can read about Server.Transfer here : http://www.dotnet-guide.com/servertransfer.html

Answer 5

You could have a global data variable that stores all your data. Each form could access it independently. If you had a multi-threaded implemenatation, you could simply add thread-safety on the accessors of the global data variable.

Answer 6

The two main options i normally use are to either store the information in a database such as SQLServer or MS-Access if there is alot of information that many forms will use, or if the information is only going to be used in the next form I would pass the information to that form and then store it as appropriate. i.e. if it create a data table for it to use as a source, store the info in a hiddenfield, or even putting the information into the text boxes, labels, combo boxes etc. that they need to go into upon loading.

Answer 7

if you are talking about winforms (not webforms) then you should probably use a static class. Use a static member to hold onto the reference of the context object (or whatever you plan to share with other forms). All static member are guaranteed to be initialized before their first use.

A similar alternative would be to use the singleton design pattern to create a singleton class.

In effect these two solutions just make it possible to access a single reference globally, which is a power that can be over used at times so... be careful.