2011-04-07 Forwarding events in C#

2011-04-07 forwarding-events-in-csharp

# Title: Forwarding events in C#
# Author: Mikael Lundin
# Link: http://blog.mikaellundin.name/2011/04/07/forwarding-events-in-csharp.html

HtmlValidator.cs

public class HtmlValidator
{
    private readonly string html;
    private XmlReaderSettings xmlValidationSettings;
 
    public HtmlValidator(string @namespace, string schemaPath)
    {
        this.html = html;
             
        /* Load the schema */
        var xmlSchema = XmlReader.Create(schemaPath);
 
        xmlValidationSettings = new XmlReaderSettings();
        xmlValidationSettings.Schemas.Add(@namespace, xmlSchema);
        xmlValidationSettings.ValidationType = ValidationType.Schema;
    }
 
    public void Validate(string html)
    {
        var htmlReader = new StringReader(html);
 
        // Trigger this event on schema validation errors
        // xmlValidationSettings.ValidationEventHandler += HandleValidationErrors; 
 
        // Read and validate htmlOutputStream
        var xmlValidatingReader = XmlReader.Create(htmlReader, xmlValidationSettings);
        while (xmlValidatingReader.Read()) ;
    }
}

OnValidationError.cs

public event ValidationEventHandler OnValidationError
{
    add { xmlValidationSettings.ValidationEventHandler += value; }
    remove { xmlValidationSettings.ValidationEventHandler -= value; }
}

Test.cs

[TestFixture]
public class Test
{
    private int CountHtmlErrors(string html)
    {
        // Create validator
        var validator = new HtmlValidator("urn:unordered-list", "UlLiSchema.xsd");
 
        // Add event handler
        var errors = 0;
        validator.OnValidationError += (o, e) => errors++;
 
        // Validate html
        validator.Validate(html);
        return errors;
    }
 
    [Test]
    public void HtmlShouldBeValid()
    {
        var html = @"<ul xmlns=""urn:unordered-list""><li></li><li></li></ul>";
 
        // Assert the result
        Assert.That(this.CountHtmlErrors(html), Is.EqualTo(0));
    }
 
    [Test]
    public void HtmlShouldBeInvalid()
    {
        var html = @"<ul xmlns=""urn:unordered-list""><p>Hello</p></ul>";
 
        // Assert the result
        Assert.That(this.CountHtmlErrors(html), Is.EqualTo(1));
    }
}