I have a Windows Forms application with a DataGridView in one of the forms. The DataGridView can insert and update through a Typed Data Set generated by Visual Studio.
I want to show user friendly error messages when a user doesnt fill in a required field or enters the wrong data type, etc. instead of the ugly huge one that is shown by default.
This page here gives some guidance. It advises me to validate input on my data sources property setters.
How can I do this with a typed dataset? I am used to working with Linq To Sql, which generated partial classes, but I am not sure about typed datasets.
Thanks.
I made a generic user-friendly error message for basic validations using this code:
dataGrid.DataError += (s, e) =>
{
if (e.Exception != null)
{
e.ThrowException = false;
MessageBox.Show(this,
String.Format("Invalid {0}",
dataGrid.Columns[e.ColumnIndex].HeaderText),
"Error");
}
};
From MSDN: Walkthrough: Handling Errors that Occur During Data Entry in the Windows Forms DataGridView Control
In terms of winforms visual feedback, I think you should look at a concept like the ErrorProvider.
If you are only focusing on input validation, like a string into an integer field this is a good approach, but please, please be aware that real validation of non-trivial mistakes shouldn't be enforced by winform's control validation event model! For example, 'EndDate < StartDate', really should be pushed down into the business layer.
Related
I’m trying to create a new dataset type Powerapps Component (PCF). For the moment I am using it to display a view of the records that are available in an entity in Microsoft Dynamics CRM.
I wish to make the view sort itself when I click on the grid column headers (in a similar way that the default CRM grid view does). I'm trying to figure out how to apply a sort to the dataset so that I can refresh it as indicated by the documentation for the dataset.refresh() function:
Refreshes the dataset based on filters, sorting, linking, new column.
New data will be pushed to control in another 'updateView' cycle.
The dataset object does have a “sorting” property, but changing its value and then refreshing the dataset doesn’t seem to have any effect. After the refresh, the sorting property reverts to the value it had before I changed it.
In short, the click handler for the grid header does something like the following bit of code. The refresh gets done and my updateView() function gets called as expected but the sorting was not applied.
dataset.sorting = [{name: 'createdon', sortDirection: 1}];
dataset.refresh();
Any help on getting the dataset sorting to work would be appreciated.
I've been experimenting with PowerApps Component Framework a little bit recently and I can confirm that the following code won't be working:
dataSet.sorting = [ { name: "columnName", sortDirection: 0 } ];
However, I managed to get this one working for me:
dataSet.sorting.pop(); // you may want to clean up the whole collection
dataSet.sorting.push({ name: "columnName", sortDirection: 0 });
I haven't really figured out the reason of this behavior. The sorting array may be implemented as some form of observable collection in the background.
I hope this will guide you to a functioning solution.
The documentation is pretty abysmal here, but here is my best guess from putting a few different pieces of information together.
TLDR: I think there is some kind of extra method that needs to be called on the .sorting property, but I can't find out what it is called. Maybe something like:
dataset.sorting.setSorting({name: 'createdon', sortDirection: 1});
I think you're going to have to try a bunch of likely method names and see what works.
Background and links:
The only reference I could find to dataset.sorting was from here:
In this preview for canvas apps, only a limited set of filtering and sortStatus methods are supported. Filter and sort can be applied to dataset on primary type columns except for the GUID. Filter and sorting can be applied in the same way as in model-driven apps.To retrieve the dataset with filtering and sorting information, call
the methods in context.parameters.[dataset_property_name].filtering
and context.parameters.[dataset_property_name].sorting, then invoke
the context.parameters.[dataset_property_name].refresh().
So it seems that the .filtering and .sorting properties are handled similarly, and that there are some methods attached to them, and only some are supported. That is about as vague as they could make it...
I did find an example of how .filtering is used:
_context.parameters.sampleDataset.filtering.setFilter({
conditions: conditionArray,
filterOperator: 1, // Or
});
There is a brief reference to .setFilter() in the docs, as well as FilterExpression
There is a SortStatus reference, but it doesn't have any corresponding methods explicitly called out. It is possible that this is not yet a supported feature in the public preview, or the documentation is lacking and the name and syntax of the method you need to call on .sorting is not yet documented.
Data validation should occur at the following places in a web-application:
Client-side: browser. To speed up user error reporting
Server-side: controller. To check if user input is syntactically valid (no sql injections, for example, valid format for all passed in fields, all required fields are filled in etc.)
Server-side: model (domain layer). To check if user input is domain-wise valid (no duplicating usernames, account balance is not negative etc.)
I am currently a DDD fan, so I have UI and Domain layers separated in my applications.
I am also trying to follow the rule, that domain model should never contain an invalid data.
So, how do you design validation mechanism in your application so that validation errors, that take place in the domain, propagate properly to the client? For example, when domain model raises an exception about duplicate username, how to correctly bind that exception to the submitted form?
Some article, that inspired this question, can be found here: http://verraes.net/2015/02/form-command-model-validation/
I've seen no such mechanisms in web frameworks known to me. What first springs into my mind is to make domain model include the name of the field, causing exception, in the exception data and then in the UI layer provide a map between form data fields and model data fields to properly show the error in it's context for a user. Is this approach valid? It looks shaky... Are there some examples of better design?
Although not exactly the same question as this one, I think the answer is the same:
Encapsulate the validation logic into a reusable class. These classes are usually called specifications, validators or rules and are part of the domain.
Now you can use these specifications in both the model and the service layer.
If your UI uses the same technology as the model, you may also be able to use the specifications there (e.g. when using NodeJS on the server, you're able to write the specs in JS and use them in the browser, too).
Edit - additional information after the chat
Create fine-grained specifications, so that you are able to display appropriate error messages if a spec fails.
Don't make business rules or specifications aware of form fields.
Only create specs for business rules, not for basic input validation tasks (e.g. checking for null).
I want to share the approach used by us in one DDD project.
We created a BaseClass having fields ErrorId &
ErrorMessage.
Every DomainModel derive from this BaseClass & thus have a two extra fields ErrorId & ErrorMessage available from
BaseClass.
Whenever exception occurs we handle exception(Log in server, take appropriate steps for compensating logic & fetch User Friendly message from client location based localized Resource file for message ) then propagate data as simple flow without raising or throwing exception.
At client side check if ErrorMessage is not null then show error.
It's basic simple approach we followed from start of project.
If it's new project this is least complicated & efficient approach, but if you doing changes in big old project this might not help as changes are big.
For validation at each field level, use Validation Application Block from Enterprise Library.
It can be used as :
Decorate domain model properties with proper attributes like:
public class AttributeCustomer
{
[NotNullValidator(MessageTemplate = "Customer must have valid no")]
[StringLengthValidator(5, RangeBoundaryType.Inclusive,
5, RangeBoundaryType.Inclusive,
MessageTemplate = "Customer no must have {3} characters.")]
[RegexValidator("[A-Z]{2}[0-9]{3}",
MessageTemplate = "Customer no must be 2 capital letters and 3 numbers.")]
public string CustomerNo { get; set; }
}
Create validator instance like:
Validator<AttributeCustomer> cusValidator =
valFactory.CreateValidator<AttributeCustomer>();
Use object & do validation as :
customer.CustomerNo = "AB123";
customer.FirstName = "Brown";
customer.LastName = "Green";
customer.BirthDate = "1980-01-01";
customer.CustomerType = "VIP";
ValidationResults valResults = cusValidator.Validate(customer);
Check Validation results as:
if (valResults.IsValid)
{
MessageBox.Show("Customer information is valid");
}
else
{
foreach (ValidationResult item in valResults)
{
// Put your validation detection logic
}
}
Code example is taken from Microsoft Enterprise Library 5.0 - Introduction to Validation Block
This links will help to understand Validation Application Block:
http://www.codeproject.com/Articles/256355/Microsoft-Enterprise-Library-Introduction-to-V
https://msdn.microsoft.com/en-in/library/ff650131.aspx
https://msdn.microsoft.com/library/cc467894.aspx
I am a newbie to knockoutjs. I have searched examples and so far no luck. I have a page that is a data collection form with the values bound using knockout. What I am trying to do is provide the user with a flag letting him know data is modified and that it needs to be saved. In the app a user may pull down the form and display the data from the server and use it only as information. In other cases he may modify that data. I want to display a label that says something like "data has been modified" to the user once any binding has changed plus if he tries to navigate away from the page I want to warn him the changes will be lost. Is there some event I can subscribe to that tells me when any value has been changed in the model?
Thanks,
Terry
Take a look at Ryan Niemeyer's Dirty Flag. It might be what you are looking for. An example of his method can be seen in this jsFiddle.
this.dirtyItems = ko.computed(function() {
return ko.utils.arrayFilter(this.items(), function(item) {
return item.dirtyFlag.isDirty();
});
}, this);
More info can be found in this SO thread: Knockout isDirty example, using dynamic viewmodule from mapping plugin
The context is as follows:
One DexExpress AspxGridView with a server-side paging/filtering/sorting mechanism (using ObjectDataSource).
I've been having problems with the filter mechanism ( see this stack ).
Now, the problem I'm having is this: the client-side events get mangled between DataSource events. :O .
Let me explain what happens: if I change the page (or sort/filter for that matter), then, select one row from the grid, the client-side SelectionChanged event fires well. If I change the page (or sort/filter), the event doesn't fire anymore. Instead, on the server side, I get a "The method or operation is not implemented" exception with the following stack-trace:
at DevExpress.Web.Data.WebDataProviderBase.GetListSouceRowValue(Int32 listSourceRowIndex, String fieldName)
at DevExpress.Web.Data.WebDataProxy.GetListSourceRowValue(Int32 listSourceRowIndex, String fieldName)
at DevExpress.Web.Data.WebDataProxy.GetKeyValueCore(Int32 index, GetKeyValueCallback getKeyValue)
at DevExpress.Web.Data.WebDataSelectionBase.GetSelectedValues(String[] fieldNames, Int32 visibleStartIndex, Int32 visibleRowCountOnPage)
at DevExpress.Web.Data.WebDataProxy.GetSelectedValues(String[] fieldNames)
at DevExpress.Web.ASPxGridView.ASPxGridView.FBSelectFieldValues(String[] args)
at DevExpress.Web.ASPxGridView.ASPxGridView.GetCallbackResultCore()
at DevExpress.Web.ASPxGridView.ASPxGridView.GetCallbackResult()
at DevExpress.Web.ASPxClasses.ASPxWebControl.System.Web.UI.ICallbackEventHandler.GetCallbackResult()
Am I doing something wrong?
Any help will be much appreciated.
suggest you avoid ObjectDataSource and do your binding in the code-behind.
You can generate your client-side code using the ObjectDataSource, and then remove it.
IMHO, ObjectDataSource and friends are not professional grade.
I'm developing a SL3 application with Prism. I need to have support for validation (both field level (on the setter of the bound property) and before save (form level)), including a validation summary, shown when the save button is pressed.
But the samples I can find googling are either SL3 with a lot of code in code behind (very uncool and un-Prismy), or WPF related.
Does anyone know a reference application with some actual validation I can look into?
Cheers,
Ali
There aren't any from Microsoft at present, but I'll pass this one onto the PRISM team tomorrow to see if we can get a basic Form Validation example inside the next rev of PRISM.
That being said, you can put a validator per Form that essentially validates each field (semantic and/or syntax validation) and should all pass, will return a true/false state.
A way I typically do this is I attach a "CanSave" method to my Commands ie:
SaveOrderCommand = new DelegateCommand<object>(this.Save, this.CanSave);
private bool CanSave(object arg)
{
return this.errors.Count == 0 && this.Quantity > 0;
}
Then in the this.CanSave, i then put either the basic validation inside this codebase, or I call a bunch of other validators depending on the context - some would be shared across all modules (ie IsEmailValid would be one Validator i place in my Infrastructure Module as a singleton and pass in my string, it would then true/false as a result). Once they all pass, ensure CanSave returns true. If they fail, the CanSave will return False.
Now if they fail and you want to trigger a friendly reminder to the user that its failed theres a number of techniques you can use here. I've typically flagged the said control at validation as being "failed".. (i wrote my own mind you, so up to you which toolkits you could use here - http://www.codeplex.com/SilverlightValidator is a not bad one).
Now, I typically like to do more with Forms that have validation on them by not only highlighting the said control (red box, icon etc) but also explain to the user in more detail whats required of them - thus custom approach is a solution I've opted for.
At the end of the day, you're going to have to do some of the heavy lifting to validate your particular form - but look into ways to re-use validators where they make sense (email, SSN etc are easy ones to re-use).
HTH?
Scott Barnes - Rich Platforms Product Manager - Microsoft.