Validation with MVVM

Hello Sorin,

Thank you for your question. I suggest that you try to use an approach suggested in our documentation: Error Notification . Does it meet your requirements?

Thank you, Marina

Hi again
I was trying not to use code behind with MVVM.
All I need it's just to validate when a TextEdit has a null EditValue.
I've attached some "code"
Thank's

Hi Sorin,

You need to validate data in the view model to make this work. If you enabled the ValidatesOnDataErrors property, you need to make the data object an implementation of the IDataErrorInfo interface. Our TextEdit supports all standard validation approaches. Please take a look at the Data Binding MSDN article to learn more about validation.

Thanks,
Ted

Based on my actual pattern I think it's impossible to validate a new item before it's inserted

Hi Sorin,

When a user types anything in the editor, the typed data should pass validation. No matter which of the approaches you will use, if validation fails, the data will not be written to the object's property. Therefore, all validation is performed before the data is inserted. Are you experiencing any trouble implementing one of the validation ways? Which one you're trying to include in your data object?

Thanks,
Ted

Hi Ted
Thank you for your patience.
Please take a look at the sample text attached before.
I need to validate when a user clicks on update button first (after using add button which makes currentItem a new object)
Because I don't want to insert null values in the database.
So I need something to call validate at update button.
Thank's

Sorin

Hi Sorin,

The data object validation is performed as soon as the binding tries to update a value. Since you set the UpdateSourceTrigger property to the "LostFocus" value, validation will be performed as soon as the editor loses focus. After that, depending on how you implemented the validation mechanism, the value will be validated in the data object and if the validation is passed, the value will be assigned to the property.
There is no way to perform validation on demand in this case.
In the "UpdCommand" Execute method, you can check whether the data object has validation errors and decide whether to save it to the database.
Therefore, everything will be implemented in the view model the way you wish.

Thanks,
Ted

Hi again
I've attached some sample about what I want to accomplish.
Thank you again.

Forgot to say I am using EF
In that sample is a simple class as database

Hi Sorin,

Thank you for the sample project. I need some time to modify it in order to illustrate how to provide the validation in a way you wish. I will get back to you as soon as possible. Please wait a while.

Thanks,
Ted

I've implemented something like here
http://stackoverflow.com/questions/3492777/validation-in-mvvm-model
If you find an easier solution please inform.
Anyway with this solution I have a problem with NullValue and/or TargetNullValue.
If I set them and the editor has a null value it displays the text. but After starting to type some text in TextEdit it remains the NullText and the new text it's appended.
Is it normal ?
Thank you