Today we're building a custom field validator. The business requirement will be simple: a lot of people at Sitecore get upset when Sitecore is spelled as "SiteCore" (oh, the joy of rebranding). We'll be making a validator to detect the incorrect capitalization and make sure items containing such atrocity never get published.

The Code

Start with the code. Here's what you should keep in mind:

1. The class should inherit from Sitecore.Data.Validators.StandardValidator.
2. The validator should be serializable: notice the [Serializable] attribute and serialization-supporting constructor.
3. Evaluate() method is responsible for the actual validation. The field value is available through the ControlValidationValue property. Return ValidationResult.Valid if no errors are found.
4. If there are errors, use the Text property to set the human-readable error description, and GetFailedResult method to return the default error value. This will allow solution architects to override the error level later (I've covered this in part 2).
5. Use the GetMaxValidatorResult method to return the maximum error level the validator can result in. Sitecore needs this to decide if your validator can potentially block a UI operation and therefore it must wait for validator to execute before the operation starts.

Now to the code:

  [Serializable]
  public class FieldValidator : StandardValidator {
    public override string Name {
      get {
        return "Sitecore capitalization validator";
      }
    }

    public FieldValidator() {}

    public FieldValidator(SerializationInfo info, StreamingContext context) : base(info, context) {}

    protected override ValidatorResult Evaluate() {
      var value = ControlValidationValue;

      if (string.IsNullOrEmpty(value)) {
        return ValidatorResult.Valid;
      }

      if (value.Contains("SiteCore")) {
        Text = "Invalid 'Sitecore' capitalization";
        return GetFailedResult(ValidatorResult.Error);
      }

      return ValidatorResult.Valid;
    }

    protected override ValidatorResult GetMaxValidatorResult() {
      return GetFailedResult(ValidatorResult.Error);
    }
  }

Registering the Validator in Sitecore

Once the validator is ready, the next step is to let Sitecore know about it. Open the /sitecore/system/settings/validation rules/field validators, create a new item using the Validation Rule template, and fill in the type field:

Now we need to setup when and where the validator should execute.

In this case we don't have to consider performance because the validation logic is simple, and we do want the validator to block workflows. So we'll enable this validator for all four scenarios for all single-line text and rich text fields in the system.

Open the /sitecore/system/settings/validation rules/field validators/field types and find the item named Rich Text.

The Rich Text will already have a number of rules set up - these are the default validations. Add the validator you've created to all of the four fields, that is the Quick Action Bar, Validate Button, Validator Bar and Workflow:

for single-line text fields (the new name for old text field) repeat the same, but you'll also need to create the Single-line text field under the field rules, because no global validators are setup for this field type by default. You can simply duplicate any existing item and remove all validators.

Action!

We're done, "SiteCore" no more:

Reusability

For a little extra reusability, this validator can easily be made configurable.

Step 1: go back to the validator definition (at /sitecore/system/settings/validation rules/field validators), and add the parameter specifying the word the validator should look for:

Step 2: update the code.

      var pattern = Parameters["Find"];
      if (value.Contains(pattern)) {
        Text = "Invalid capitalization";
        return GetFailedResult(ValidatorResult.Error);
      }

Notice the usage of Parameters dictionary instead of the hardcoded value. That's it.

Next

I promise, next part will be the last, and we'll build an action that fixes the errors automatically in the single-line text field.

This post is a part of series about new validation features introduced in Sitecore 6:

Part 1: Introduction, configuration, validation types.
Part 2: Error levels, built-in validators.
Part 3: Making a custom validator.
Part 4: Making a validator fix action.