I have a table in SQL that I want to read into a DataGrid.
When I insert a new element I would like the DataGrid to update automatically.
Currently I manually do a SQL query and create a custom object that represents the objects in my SQL.
I am wondering whether I could use DataBinding but also maintain some control over how the data is read in? Because I'd like to have a local model to work with. Or is it just simpler to manually redownload the table after every insert?
Thanks
Yes of course. Using Entity framework, to pull the data, and then bind it to a control (or a complex form with many tabs) - and allowing the EF to do all the hard work for You is the way to go ...
Just imagine - if You have a complex model with a lot of controls, and when You hit save.. it just does that and generates as many inserts or updates for you.
with just one line of code. Context.SaveChanges :)
Related
I have just added a IsValidRecord column to a MyClass SQL table.
It will be used as a logical delete / soft delete.
Now I need to update my application to only query the valid records based on the new column.
I use Entity Frameword DB first.
Our app uses a business layer that centralizes all methods fetching the MyClass items.
So I have updated all the methods that query the concerned table with the appropriate filter based on IsValid.
It works fine.
However, I am pretty sure that these are bad practises because devs will forget to set this filter on new methods that will be added in the future, which will obviously bring incorrect records.
I wonder if EF would have features to automatically filter the queries with the appropriate "AND IsValid = 1" filter?
I used to be working for a company doing the same with NHibernate.
The only supported feature that I have seen for EF is this:
Soft Delete
Unfortunately,it overwrites OnModelCreating so I take it that it only works for Code First architecture.
We use DataBase first so I think it does not work as OnModelCreating is never called?
I would normally implement this filter using application-specific views in the database (after all, some uses of this data may need to be able to see deleted items).
With a simple definition for the view, they should automatically be considered updatable by SQL so you shouldn't need to have to write triggers to manage INSERT/UPDATE/DELETE operations. You then lie to Entity Framework about what its "tables" are and it should mostly be none-the-wiser.
Depending on how you want the soft-delete to work, you may choose to hide the existence of the IsValidRow column (nit: we have rows in SQL, not records) in this view and implement an INSTEAD OF DELETE trigger on the view allowing your application to soft delete these rows by asking EF to remove them.
The best link I have found is this:
EDMX Mapping
Use EDMX designer to add the filter condition. It's basically exacly what I want...
Are there any down sides for this solution?
At first sight, it sounds good enough to me.
Only disadvantage that I can think of is that the filter is well hidden. Other devs in the future might have very hard time to figure out why / where / how are the entities filtered.
I have recently decided to re-develop an access VBA application in VB .net with DevExpress.
I have managed to figure out databinding with the raw tables. However, I am struggling with the queries.
I have tried the query builder, but I dont have the option to save them and bind object to it. I assume it works this way? As it did in access? Or is the query builder there simply to help you format the SQL text?
I am trying to bind a DataGrid to a simply join query without any luck.
Can you someone point me in the right direction?
Thanks.
There are two main approaches that I can think of. One is to use datatables, and the other is to use domain objects.
Datatables are quick to write, can easily handle most of the heavy lifting for you (including CRUD operations) and are pretty scalable, as changes to the underlying object can be handled relatively easily.
DataTable dt = new DataTable();
Domain Objects (aka POCOs) take a lot of up-front work but typically in the log run make for a more bulletproof and robust solution. Plus, there are frameworks and even Micro ORMs that will do much of the heavy lifting for you, if you choose to use them.
List<DomainObject> do = new List<DomainObject>();
These work with tables, views or queries. You mention you have this figured out for a table, so I'm guessing you have already sort-of gotten this far.
So, first step -- figure out which direction you want to go. (pick domain objects)
Second step -- I recommend using a binding source (System.Windows.Forms.BindingSource). Make your data table / collection the DataSource for the binding source.
Third step, make the binding source the data source for your grid. If you are using a Domain Object, you'll see the columns populate automatically.
From there, once the datatable or collection is populated, you can assign it as the data source for the binding source, and .NET and Dev Express will take care of the rest for you.
bindingSource1.DataSource = dt;
or
bindingSource1.DataSource = do;
Now if you're talking CRUD operations -- that's a horse of a different color. You still use these as building blocks, but this is in no way a comprehensive answer for that.
By the way, the code above is C#, so you need minor tweaks to get this to be VB. I don't speak VB, otherwise I would have just done it like that to begin with.
I'm interested in displaying 1-5 model instances using forms on a page using a grid similar to something one would find in a desktop database application. I understand I would need to use multiple forms or formsets but an additional requirement is that I'd prefer it to be in more of a grid format with each model's fields being display in columns with common field labels on the y-axis.
I should have the ability to edit multiple columns (so in effect, model instances) at the same time and then commit either the single column (model instance) or commit all. I'd also like to be able to highlight the changed cells that have changed to give visual feedback to the user that there are pending changes.
Sorry for the rather long list of requirements and I'm aware this probably requires a few different technologies/techniques to achieve. I'm throwing this out there because I'm asking this kind community for guidance on what components/technologies I should look at. If luck would have it, there would be some jQuery component that can handle this for me almost out of the box. If not, some guidance on achieving the editing of multiple model instances would be of help.
I will also need to build in versioning in case the data displayed on the view page is stale and to prevent overwriting a newer commit. I'd probably achieve the latter using a versioning field in the table that will perform the check and handle it accordingly.
Also, Flask and Django are both options for the engine and WTForms look to be promising at least at first look.
Thanks
There is no such ready to use solution in Django. Just create your custom form that handles as many instances as you want and do anything that you want, or extend formset.
Is there a quick and easy way to make a VB.NET user interface for managing the data in a normalized DataSet?
I know that is a very subjective question, so let me explain. For a brief period early in my career, I used to create user interfaces in Microsoft Access. I developed a simple, but very effective approach to user interface design. Here are some details of that approach:
Create one form per table. Put on
each form all controls necessary to
completely manage one row in the
table.
Use combo boxes for
foreign-key columns.
Give the user a
standard way to add rows and delete
rows.
Use Apply and Undo buttons.
Let
the user navigate from one row to
another with a list box.
Provide a
search box and filter options for
more efficient navigation.
Let the
user double-click on controls
representing foreign-key columns to
quickly navigate from one form to
another.
Make the state of each form
persistent (so the user always
returns to the last navigation point)
etc.
Simple, right? I found that Access encouraged this approach. It has many built-in features that make this kind of UI easy. For instance, creating a combo box to represent a foreign key relationship takes about 10 seconds.
Well, I haven't worked in Access for a while. A couple of years ago, however, I was hired to write an application in VB.NET on the NET 2.0 framework. To get a data management user interface up and running quickly, I used my Access experience to write a quick & easy prototype in Access -- that took me about one week. Then I hired a programmer to implement that same UI in VB.NET. What a nightmare! We've been working on that implementation for a year, and I'm still very unsatisfied with the results. Some of the problems we are having:
Apply and Undo buttons don't work quite right. We can't find an event that tells us when the form is "dirty" (thus making Apply and Undo relevant).
Navigation from row to row and from form to form requires surprisingly complicated code. I get the impression that we are fighting against NET's binding features, not working with them the way they were intended to be used.
The NET controls seem buggy. For instance, when the user types a value into a combo box (as opposed to choosing it from the drop down), it doesn't trigger the SelectedValueChanged event.
We seem to be repeating a lot of information. For instance, the DataSet knows there is a relationship between the columns in two tables, but we must nevertheless effectively repeat the details of that relationship when we program the combo boxes, binding, navigtation features, etc.
We still don't have good solutions for the filter and search features. There are lots of little details to work out. (For instance, what if you choose a filter that doesn't include the currently displayed row?)
We are writing many helper functions and classes to simplify the work, and I can't figure out why that effort hasn't already been done by others -- I'm certain we are reinventing the wheel.
etc.
By themselves, none of the above are a big deal -- there are effective solutions to each one. Taken together, however, these problems are making my UI development go much slower than expected.
In an ideal world, I should be able to create a small amount of code relevant to my specific data model (for instance, one user control per table establishing the layout and logic relevant to the rows in that table) then integrate that code into a template which interprets the data model and handles everything else -- navigation, adding and deleting, apply and undo, search and filter, etc.
Thus, my question: Is there anything out there which makes this type of UI development easier?
I've searched the web for various combinations of "generic forms", "UI templates", "data managment forms", etc., but I haven't found anything on topic. Perhaps I just don't know the buzzwords. Is there a specific name for this type of UI development task?
Create UCs for each table. Drop a grid control onto the UC and bind it to the tables dataset using VS's wizard. Select the options that allow for insert, update, delete. Each row on the grid will have those buttons/actions automatically added for you.
I have recently written an application(vb.net) that stores and allows searching for old council plans.
Now while the application works well, the other day I was having a look at the routine that I use to generate the SQL string to pass the database and frankly, it was bad.
I was just posting a question here to see if anyone else has a better way of doing this.
What I have is a form with a bunch of controls ranging from text boxes to radio buttons, each of these controls are like database filters and when the user hits search button, a SQL string(I would really like it to be a LINQ query because I have changed to LINQ to SQL) gets generated from the completed controls and run.
The problem that I am having is matching each one of these controls to a field in the database and generating a LINQ query efficiently without doing a bunch of "if ...then...else." statements. In the past I have just used the tag property on the control to link to control to a field name in the database.
I'm sorry if this is a bit confusing, its a bit hard to describe. Just throwing it out there to see if anyone has any ideas.
Thanks
Nathan
When programming complex ad-hoc query type things, attributes can be your best friend. Take a more declarative approach and decorate your classes, interfaces, and/or properties with some custom attributes, then write some generic "glue" code that binds your UI to your model. This will allow your model and presentation to be flexible, without having to change 1000s of lines of controller logic. In fact, this is precisely how Microsoft build the Visual Studio "Properties" page. You may even be able use Microsoft's "EnvDTE.dll" in your product depending on the requirements.
You could maybe wrap each control in a usercontrol that can take in IQueryable and tack on to the query if it is warranted.
So your page code might go something like
var qry = from t in _db.TableName
select t;
then pass qry to a method on each user control
IQueryable<t> addToQueryIfNeeded(IQueryable<t> qry)
{
if(should be added)
return from t in qry
where this == that
select t;
else
return qry
}
then after you go through each control your query would be complete and then you can .ToList() it. A cool thing about LINQ is nothing happens until you .ToList() or .First() it.
I don't know about the performance here, but if you set up the LINQ to SQL data context class you should be able to query a database table with a .Select(...) or .Where(...). You should be able to build lambda expressions for either of these dynamically. You might look into dynamic generation of lambda expressions for this purposes. I have done everything up to the point of the dynamic lambda generation, but it is possible.
I'm not 100% sure how to achieve this but I know where a good place to start would be, in the ASP.NET MVC source. In recent versions it is capable of taking the form response and pass it into a helper method which does the writing to a LINQ data source.
I believe MVC is C# so if you're looking for a VB translation you could try using .NET Reflector and converting it back to VB.
I think you are searching how to create a "Dynamic" Linq Query, Here is an example about how to do it with a library of extension methods. Those methods take string arguments instead of type-safe language operators.
I don't mind sfusco's method by using attributes. The only thing that i'm not sure of is where to attach the attributes to because If I attach then to the controls declaration which is in the designer code it will get regenerated when the form changes.
Or am I completely misunderstanding sfusco's methods?
I think perhaps the right way to do this would be an extender provider: MSDN documentation
Then, you can use the editor to provide the field names to hook up with, and your extender provider can be passed an IQueryable<T>, add the criteria, and return an IQueryable<T>.