CODEWITHSUNDEEP
c#wpfmvvmdatagrid
staticshockdracoon
staticshockdracoon

Reputation: 41

Dynamic column datagrid in wpf

I have a case where in the columns of Datagrid are not fixed . i.e it has to be generated depending on some conditions.

How can i store the values in the DB and display the datagrid with them using MVVM pattern.

P.S : I have a main grid and a sub grid and depending on the value he chooses in the main grid i need to form the below grid. My concern also in storing it in the DB, since there can be 5 columns or sometimes 20.

Any similar links or references will also be useful.

Upvotes: 0

Views: 373

Answers (1)

slugster
slugster

Reputation: 49965

This can be totally done in an MVVM compliant way, but isn't necessarily trivial for a beginner, and isn't appropriate for simple applications.

One approach I like to use is to keep a collection of column descriptors serialised in the database1. The column descriptors are simply my own custom DTO data classes and contain properties related to a column, i.e. width, column type, whether it is visible, whether it's visibility can be toggled, it's ordinal, etc. This is all done using simple structs and or primitive .Net types, but specifically doesn't have any UI related data types in it at all2.

This list of ColumnDescriptors can then be serialiased to and from XML, and stored in the database either in an nvarchar or XML column. Especially on SQL Server an XML column is better as you can natively query deep into the XML structures stored in the database column.

As it is a UI layout thing, it is up to the view to query the right set of column descriptors from the database, I then pump that collection through a static GridColumnFactory class which iterates the descriptor objects and creates me the appropriate grid columns and assigns the appropriate values to them. Once the factory returns that collection the view can then add them to the DataGrid's columns collection.

The benefits of this approach:

  • If I swap out the DataGrid that is used (i.e. swap from one vendor to another, say DevExpress to ComponentOne or native WPF), I can simply change the types of columns returned from the factory class

  • If I swap anything in the UI then I don't need to touch the column descriptors that are stored.

  • Serialising to and from XML means that if I do add/remove properties from the descriptors then older stored copies can still be accommodated, they aren't instantly broken the moment I release an update

  • One of the best features of all is that I can change the stored column layouts with a simple SQL statement, I don't have to also release compiled code

  • One last thing - using column descriptors makes it trivial to implement a user specified layout, i.e. when you let them drag columns around and then want to save the layout for next time

  • If I want to get really funky, the column descriptors can be returned from a webservice

1 For a website these could also be stored in a loose XML file which is then read in and kept in cache.

2 For this approach you should always avoid using specialised or vendor specific data types, as they don't necessarily serialise well (if at all), and will become a weak point in the future - these will be the most likely things you have to change, and if these change you break any stored descriptors you've already got.

Upvotes: 2

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