Make Gridview interact with something other than properties

Question

We're planning to create a web application where users can build custom "forms," choosing which fields they would like, and how the data in those fields should be represented. Users can then fill out these forms in a DetailsView-like control, thereby creating "documents." The documents can be shown in a DetailsView, or certain fields of several of them can be shown in a GridView. At least, that's the idea.

The problem is that GridView and DetailsView seem to be specifically designed to access Properties on objects that come out of a DataSource. Since we want to have completely arbitrary forms, we can't restrict ourselves to building a class with Properties to represent each field. We have to be able to have any number of dynamically-specified fields on a form.

Is there any way to leverage the existing controls so we don't have to re-implement paging, sorting, and all the other things that GridViews are already set up to do, or will I just have to create my own GridView-like control from scratch?

Edit:

More specifically, the difficulty I am having is in getting inline editing to work on the GridView. For example, let's say that one of the "fields" that is added to a "form" is a calendar field, which should display a date as text in read-only mode, and display a calendar control in edit mode. When the "save" button is clicked, the date selected by the calendar control needs to be saved to the database as the new value for the given field of the given document (i.e. instance of the form). My initial idea was to create a special DataControlField class which, given a form field key, would know how to databind thusly:

FormDocument doc = DataBinder.GetDataItem(cell) as FormDocument;
FormFieldValue fieldValue = doc.FieldValues[FieldKey];
fieldValue.AddReadOnlyControls(cell);

... instead of:

Object dataObject = DataBinder.GetDataItem(cell);
cell.Text = DataBinder.GetPropertyValue(dataItem, FieldKey);

This would probably work for displaying the field values, but if the user tries to edit and save one of the FormDocuments I don't know how I would convince the GridView to do something like this:

doc.FieldValues[FieldKey] = newValue;

Currently, the API for DataControlField uses the ExtractValuesFromCell method to put the property name and value into an IOrderedDictionary. Those values are then applied to the given properties of the objects in the GridView's databound IEnumerable. The problem is, I can't work with properties of an object because in this case the object needs to have a completely arbitrary number of fields.

Answer 1

A GridView can be bound to any object that implements IEnumerable. The advantage of using one of the xDataSource controls is that it can implement paging and sorting for you without any additional code, but you certainly aren't tied to them.

If I understand your question correctly, you do not know the number of columns to display in the GridView until runtime. In that case, I would recommend building an array from your form data and binding the grid to that. You will have to implement paging and sorting yourself.

The DetailsView is not very customizable so you should take a look at the FormView. However, I think you are going to end up dynamically adding controls to whatever container you use.

Answer 2

Hi ,

What you need is totally dynamic GridView. I quess you would have to extend it with the controls ( functionalities ) in your description

Answer 3

Here's what I ended up doing:

1. I created a new data type that contained a Dictionary of answers, indexed by Field ID.
2. I created a new type of DataControlField with a FieldId property, which retrieves the proper answer value for that FieldId from the Dictionary mentioned above.
3. I added data type and data keys properties to this custom DataControlField and overrode the ExtractValuesFromCell method so that it could create a new instance of the answer class and add those values to a Dictionary, which was stored under the property name by which that dictionary would be found in the new data type mentioned in step 1.
4. I used my own GridView class, used the .NET Reflector to see how the normal GridView calls the ExtractValuesFromCell method, and then changed that so that it would pass the same Dictionary object in to each DataControlField. This way, each field could add to the same Dictionary, rather than replacing the Dictionary that the last one had added under the same property name.
5. I used a DataFieldGenerator to generate the one of my custom DataControlFields for every field associated with a given form, and I told the GridView to use that DataFieldGenerator to auto-generate its fields.
6. I set up my ObjectDataSource so that it would know how to save all the answer values from an object of the type mentioned in step 1.

It was tricky, but worthwhile.