Wpf textbox validating
Is Valid() method and in-fact is internal in Silverlight. Anyways, here’s the code for our Validate() method in our Validation View Model base class. Get Validation Result(): So, what we are doing here is iterating through all of the validators defined on properties in our view-model and passing each of them the current value of the property which we are validating as well as the Validation Context, which in this example we have only set the Object Instance to `this´.
I chose to make this a property and set it in the Validation View Model constructor: Now, for the actual cross-field validation itself let’s move on to our Required If Attribute implementation of Validation Attribute.
Get Validation Result() method and the Validation Context class.field A should only be validated if field B is true) using nothing but attributes (and of course a little bit of helper code, which I’ll give you). Before you get started, you need to add a reference to the System. To change the mode, you can set the property `Use Explicit Validation´ in your view-model constructor (or change it at any time elsewhere).The idea behind this is to be able to do something like this: Looking at the [Required If(...)] attribute, simply put it means: “`Last Name´ is required if the property `Is Last Name Required´ equals true. Okay, let’s have a look at our view-model and the XAML for the window we will be binding to the view-model: Main Window View Note that in the constructor I am setting `Use Explicit Validation´ to true, and also that I am raising the `On Property Changed´ event each time a property is set.When validation fails, the error message to display is `Last name is required.´”. Raising the Property Changed event is very important to ensure that binding works and for the framework to know when a property has changed.
Since we’re using some Text Box controls it might be worth mentioning that Text Box.
At one point or another we’ve all had to do some sort of input validation. This is where Validation Attribute and the framework-provided implementations exist.