When errors occur the form should preserve the input data the user originally entered so that they don't have to refill their changes manually.
This process should repeat as many times as necessary until the form successfully completes. To see these features in action let's update our Edit action method with the following code:. If an exception occurs either when calling UpdateModel , or when we try and save the DinnerRepository which will raise an exception if the Dinner object we are trying to save is invalid because of a rule violation within our model , our catch error handling block will execute.
Within it we loop over any rule violations that exist in the Dinner object and add them to a ModelState object which we'll discuss shortly. We then redisplay the view. Our application has a decent error experience. The text elements with the invalid input are highlighted in red, and validation error messages are displayed to the end user about them.
The form is also preserving the input data the user originally entered — so that they don't have to refill anything. How, you might ask, did this occur? How did the Title, EventDate, and ContactPhone textboxes highlight themselves in red and know to output the originally entered user values? And how did error messages get displayed in the list at the top? The good news is that this didn't occur by magic - rather it was because we used some of the built-in ASP.
Controller classes have a "ModelState" property collection which provides a way to indicate that errors exist with a model object being passed to a View. Error entries within the ModelState collection identify the name of the model property with the issue for example: "Title", "EventDate", or "ContactPhone" , and allow a human-friendly error message to be specified for example: "Title is required".
The UpdateModel helper method automatically populates the ModelState collection when it encounters errors while trying to assign form values to properties on the model object. When the UpdateModel method was unable to assign the string value "BOGUS" to it in the scenario above, the UpdateModel method added an entry to the ModelState collection indicating an assignment error had occurred with that property.
Developers can also write code to explicitly add error entries into the ModelState collection like we are doing below within our "catch" error handling block, which is populating the ModelState collection with entries based on the active Rule Violations in the Dinner object:.
HTML helper methods - like Html. TextBox - check the ModelState collection when rendering output. If an error for the item exists, they render the user-entered value and a CSS error class.
For example, in our "Edit" view we are using the Html. TextBox helper method to render the EventDate of our Dinner object:. When the view was rendered in the error scenario, the Html. TextBox method checked the ModelState collection to see if there were any errors associated with the "EventDate" property of our Dinner object. You can customize the appearance of the css error class to look however you want.
ValidationMessage helper method can be used to output the ModelState error message associated with a particular model property:. ValidationMessage helper method also supports a second parameter that allows developers to override the error text message that is displayed:. ValidationSummary helper method takes an optional string parameter — which defines a summary error message to display above the list of detailed errors:. We can make this code a little cleaner by adding a "ControllerHelpers" class to the NerdDinner project, and implement an "AddRuleViolations" extension method within it that adds a helper method to the ASP.
This extension method can encapsulate the logic necessary to populate the ModelStateDictionary with a list of RuleViolation errors:. The nice thing about our Edit implementation is that neither our Controller class nor our View template has to know anything about the specific validation or business rules being enforced by our Dinner model.
We can add additional rules to our model in the future and do not have to make any code changes to our controller or view in order for them to be supported. This provides us with the flexibility to easily evolve our application requirements in the future with a minimum of code changes. We've finished implementing the "Edit" behavior of our DinnersController class.
Let's now move on to implement the "Create" support on it — which will enable users to add new Dinners. Our implementation looks like:. The code above creates a new Dinner object, and assigns its EventDate property to be one week in the future.
It then renders a View that is based on the new Dinner object. Viewed 59k times. Improve this question. Rizwan Safdar Rizwan Safdar 2 2 gold badges 2 2 silver badges 11 11 bronze badges. Add a comment. Active Oldest Votes. Improve this answer. Linger Linger Unbound controls will not have any database fields to update. So, Me.
But, you wouldn't need it to. Unbound controls are controlled via an action to another control or user interaction. Edit: If you want to change an unbound control value programmatically: myForm.
Philippe Grondier Philippe Grondier As far as I remember, it depends how you are loosing the focus: if it's through ESC key, update might not be fired. If it's through Enter or TAB, it will be fired. The Invalidate method governs what gets painted or repainted. The Update method governs when the painting or repainting occurs. If you use the Invalidate and Update methods together rather than calling Refresh , what gets repainted depends on which overload of Invalidate you use. The Update method just forces the control to be painted immediately, but the Invalidate method governs what gets painted when you call the Update method.
Skip to main content. You can use the Refresh method to view changes that have been made to the current set of records in a form or datasheet since the record source underlying the form or datasheet was last refreshed.
In an Access database, the Refresh method shows only changes made to records in the current set. Because the Refresh method doesn't actually requery the database, the current set won't include records that have been added or exclude records that have been deleted since the database was last requeried, nor will it exclude records that no longer satisfy the criteria of the query or filter.
To requery the database, use the Requery method. When the record source for a form is requeried, the current set of records will accurately reflect all data in the record source.
In an Access project.
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