![]() ![]() Protected override ValidationResult IsValid(object value, ValidationContext validationContext) Public RequiredIfAttribute(string propertyName, object value = null, string errorMessage = "") Public class RequiredIfAttribute : ValidationAttribute I wrote a simple custom validation attribute that it's very readable. NET 5, but I tried to remove language features added in c# 9.0 for wider compatibility. This way, you get all the standard Required validation features. Return base.IsValid(value, validationContext) IsInverted & !Equals(actualOtherPropertyValue, OtherPropertyValue)) If (!IsInverted & Equals(actualOtherPropertyValue, OtherPropertyValue) || GetValue(validationContext.ObjectInstance, null) Object actualOtherPropertyValue = otherPropertyInfo ValidationContext.ObjectType, OtherProperty)) PropertyInfo otherPropertyInfo = validationContext Protected override ValidationResult IsValid( Public RequiredIfAttribute(string otherProperty, object otherPropertyValue) / Initializes a new instance of the class. / Gets or sets the other property name that will be used during validation. Public sealed class RequiredIfAttribute : ValidationAttribute / Provides conditional validation based on related property value. Typing a single letter in the Title field satisfies the validation requirements, so the validation message is immediately removed.I've written a RequiredIfAttribute that requires a particular property value when a different property has a certain value (what you require) or when a different property has anything but a specific value. We are wasting server resources to perform validation logic instead of leveraging the user's browser.įortunately, the ASP.NET MVC 3 scaffold templates have client-side validation built in, requiring no additional work whatsoever.The user doesn't get immediate feedback when they correct a field so that it now passes the validation rules.The user has to wait for the form to be posted, validated on the server, and for the response to be sent to their browser.However, webpage forms which only implement server-side validation exhibit three significant problems. Server-side validation is very important from an application perspective, because users can circumvent client-side validation. When we click on the Create button, we will see the form displayed with validation error messages showing which fields did not meet the validation rules we have defined. Enter a price of 0 and leave the Title blank. Run the application and browse to /StoreManager/Create. Public virtual Artist Artist Īfter having added these attributes to our Album model, our Create and Edit screen immediately begin validating fields and using the Display Names we've chosen (e.g. namespace MvcMusicStore.ModelsĮrrorMessage = "Price must be between 0.01 and 100.00")] Next, update the properties to add display and validation attributes as shown below. Open the Album class and add the following using statements to the top. *Note: For more information on Model Validation using Data Annotation attributes, see the MSDN documentation at * ScaffoldColumn – Allows hiding fields from editor forms.Bind – Lists fields to exclude or include when binding parameter or form values to model properties.Range – Gives a maximum and minimum value for a numeric field.StringLength – Defines a maximum length for a string field.DisplayName – Defines the text to use on form fields and validation messages.Required – Indicates that the property is a required field.We'll use the following Data Annotation attributes: Data Annotations allow us to describe the rules we want applied to our model properties, and ASP.NET MVC will take care of enforcing them and displaying appropriate messages to our users. We can easily add validation to our application by adding Data Annotations to our model classes. We can do things like leave required fields blank or type letters in the Price field, and the first error we'll see is from the database. We have a major issue with our Create and Edit forms: they're not doing any validation. ![]() ![]() Part 6 covers Using Data Annotations for Model Validation. This tutorial series details all of the steps taken to build the ASP.NET MVC Music Store sample application. The MVC Music Store is a lightweight sample store implementation which sells music albums online, and implements basic site administration, user sign-in, and shopping cart functionality. The MVC Music Store is a tutorial application that introduces and explains step-by-step how to use ASP.NET MVC and Visual Studio for web development. ![]()
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