(Thanks to [Ted & Gustaf](🔗) for this example.)
One usage scenario could be to check for a cookie that says that the visitor has previously completed a purchase on the website; that is, is a returning customer.
## Create the settings and criterion classes
All visitor group criteria require a `
settings` class and a `
settings` class is used to persist any settings available to editors when creating new visitor groups.
criterion` class contains the logic to determine whether or not a visitor belongs to the visitor group.
You should create the two classes in a suitable folder structure:
## Implement the settings class
The only setting required for this visitor group criterion is the cookie name you should look for.
First, make the `
CookieExistsCriterionSettings` class inherit the `
Add a public property to let editors specify the cookie name:
If you need custom validation logic when a criterion is saved, you can make your settings class implement the `
IValidateCriterionModel` interface (this is optional). By implementing that interface’s `
Validate` method, you can customize how settings are validated before saving a criterion for a visitor group.
The abstract `
CriterionModelBase` class requires you to implement the `
Copy()` method. Because you are not using complex reference types, you can implement it by returning a shallow copy as shown (see [Create custom visitor group criteria](🔗)):
This is the complete `
## Implement the criterion class
Make the `
CookieExistsCriterionclass` inherit the abstract `
CriterionBaseclass` with the settings class as the type parameter:
Add a `
VisitorGroupCriterion` attribute to set the category, name, and description of our criterion (for more available `
VisitorGroupCriterion` properties, see [Create custom visitor group criteria](🔗):
The abstract `
CriterionBase` class requires you to implement an `
IsMatch()` method which determines whether the current user matches this visitor group criterion. You should check if a specific cookie exists based on the criterion settings:
The criterion class appears as follows:
You access the criterion settings instance through the Modelproperty.
## Test the new criterion
To test the criterion, create a new visitor group using the new cookie criterion.
Set the cookie name to **.EPiServerLogin**, the name of the cookie created when a user logs in:
If you are on CMS version 10 or 11, it will look like this:
Select some content in the editor that should only be displayed to users currently logged in to Episerver.
Click **Personalized Content** and select the new **Episerver User** visitor group.
This content is now only displayed to users logged into Episerver:
After publishing the page, you see this:
However, if you log out, you no longer see the personalized content.