public static class StandardDeviationExtensions
{
    public static double SampleStandardDeviation(this IEnumerable<double> values)
    {
        int count = values.Count();
 
        if (count > 1)
        {
            double average = values.Average();
            double sumOfSquaredDifferences = values.Sum(v => Math.Pow(v - average, 2));
            return Math.Sqrt(sumOfSquaredDifferences / (count - 1));
        }
 
        return 0.0;
    }
 
    public static double PopulationStandardDeviation(this IEnumerable<double> values)
    {
        if (values.Count() > 1)
        {
            double average = values.Average();
            return Math.Sqrt(values.Average(v => Math.Pow(v - average, 2)));
        }
 
        return 0.0;
    }
 
    public static TimeSpan SampleStandardDeviation(this IEnumerable<TimeSpan> values)
    {
        return new TimeSpan(
            (long)values
                .Select(v => (double)v.Ticks)
                .SampleStandardDeviation());
    }
 
    public static TimeSpan PopulationStandardDeviation(this IEnumerable<TimeSpan> values)
    {
        return new TimeSpan(
            (long)values
                .Select(v => (double)v.Ticks)
                .PopulationStandardDeviation());
    }
}

[TestClass]
public class StandardDeviationTest
{
    private readonly double[] EmptySet = new double[] {};
    private readonly double[] SingleValue = new double[] { 1.0 };
    private readonly double[] SameValues = new double[] { 5.0, 5.0, 5.0 };
    private readonly double[] ScenarioValues = new double[] { 2.0, 4.0, 4.0, 4.0, 5.0, 5.0, 7.0, 9.0 };
 
    private const double ScenarioValuesSampleDeviation = 2.13809;
    private const double ScenarioValuesPopulationDeviation = 2.0;
 
    [TestMethod]
    public void SampleStandardDeviation_EmptySet_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, EmptySet.SampleStandardDeviation());
    }
 
    [TestMethod]
    public void SampleStandardDeviation_SingleValue_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, SingleValue.SampleStandardDeviation());
    }
 
    [TestMethod]
    public void SampleStandardDeviation_SetOfSameValues_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, SameValues.SampleStandardDeviation());
    }
 
    [TestMethod]
    public void SampleStandardDeviation_ScenarioValues_HaveExpectedDeviation()
    {
        Assert.AreEqual(ScenarioValuesSampleDeviation, Math.Round(ScenarioValues.SampleStandardDeviation(), 5));
    }
 
    [TestMethod]
    public void SampleStandardDeviation_TimeSpanScenarioValues_HaveExpectedDeviation()
    {
        var timeSpanValues = ScenarioValues.Select(seconds => new TimeSpan(0, 0, (int)seconds));
        var result = timeSpanValues.SampleStandardDeviation().TotalSeconds;
        Assert.AreEqual(ScenarioValuesSampleDeviation, Math.Round(result, 5));
    }
 
    [TestMethod]
    public void PopulationStandardDeviation_EmptySet_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, EmptySet.PopulationStandardDeviation());
    }
 
    [TestMethod]
    public void PopulationStandardDeviation_SingleValue_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, SingleValue.PopulationStandardDeviation());
    }
 
    [TestMethod]
    public void PopulationStandardDeviation_SetOfSameValues_HasZeroDeviation()
    {
        Assert.AreEqual(0.0, SameValues.PopulationStandardDeviation());
    }
 
    [TestMethod]
    public void PopulationStandardDeviation_ScenarioValues_HaveExpectedDeviation()
    {
        Assert.AreEqual(ScenarioValuesPopulationDeviation, Math.Round(ScenarioValues.PopulationStandardDeviation(), 5));
    }
 
    [TestMethod]
    public void PopulationStandardDeviation_TimeSpanScenarioValues_HaveExpectedDeviation()
    {
        var timeSpanValues = ScenarioValues.Select(seconds => new TimeSpan(0, 0, (int)seconds));
        var result = timeSpanValues.PopulationStandardDeviation().TotalSeconds;
        Assert.AreEqual(ScenarioValuesPopulationDeviation, Math.Round(result, 5));
    }
}

WebClient client = new WebClient();
string html = client.DownloadString(@"http://www.table.co.uk");
DataSet dataSet = HtmlTableParser.Parse(html);

/// <summary>
/// HtmlTableParser parses the contents of an html string into a System.Data DataSet or DataTable.
/// </summary>
public class HtmlTableParser
{
    private const RegexOptions ExpressionOptions = RegexOptions.Singleline | RegexOptions.Multiline | RegexOptions.IgnoreCase;
 
    private const string CommentPattern = "<!--(.*?)-->";
    private const string TablePattern = "<table[^>]*>(.*?)</table>";
    private const string HeaderPattern = "<th[^>]*>(.*?)</th>";
    private const string RowPattern = "<tr[^>]*>(.*?)</tr>";
    private const string CellPattern = "<td[^>]*>(.*?)</td>";
 
    /// <summary>
    /// Given an HTML string containing n table tables, parse them into a DataSet containing n DataTables.
    /// </summary>
    /// <param name="html">An HTML string containing n HTML tables</param>
    /// <returns>A DataSet containing a DataTable for each HTML table in the input HTML</returns>
    public static DataSet ParseDataSet(string html)
    {
        DataSet dataSet = new DataSet();
        MatchCollection tableMatches = Regex.Matches(
            WithoutComments(html),
            TablePattern,
            ExpressionOptions);
 
        foreach (Match tableMatch in tableMatches)
        {
            dataSet.Tables.Add(ParseTable(tableMatch.Value));
        }
 
        return dataSet;
    }
 
    /// <summary>
    /// Given an HTML string containing a single table, parse that table to form a DataTable.
    /// </summary>
    /// <param name="tableHtml">An HTML string containing a single HTML table</param>
    /// <returns>A DataTable which matches the input HTML table</returns>
    public static DataTable ParseTable(string tableHtml)
    {
        string tableHtmlWithoutComments = WithoutComments(tableHtml);
 
        DataTable dataTable = new DataTable();
 
        MatchCollection rowMatches = Regex.Matches(
            tableHtmlWithoutComments,
            RowPattern,
            ExpressionOptions);
 
        dataTable.Columns.AddRange(tableHtmlWithoutComments.Contains("<th")
                                       ? ParseColumns(tableHtml)
                                       : GenerateColumns(rowMatches));
 
        ParseRows(rowMatches, dataTable);
 
        return dataTable;
    }
 
    /// <summary>
    /// Strip comments from an HTML stirng
    /// </summary>
    /// <param name="html">An HTML string potentially containing comments</param>
    /// <returns>The input HTML string with comments removed</returns>
    private static string WithoutComments(string html)
    {
        return Regex.Replace(html, CommentPattern, string.Empty, ExpressionOptions);
    }
 
    /// <summary>
    /// Add a row to the input DataTable for each row match in the input MatchCollection
    /// </summary>
    /// <param name="rowMatches">A collection of all the rows to add to the DataTable</param>
    /// <param name="dataTable">The DataTable to which we add rows</param>
    private static void ParseRows(MatchCollection rowMatches, DataTable dataTable)
    {
        foreach (Match rowMatch in rowMatches)
        {
            // if the row contains header tags don't use it - it is a header not a row
            if (!rowMatch.Value.Contains("<th"))
            {
                DataRow dataRow = dataTable.NewRow();
 
                MatchCollection cellMatches = Regex.Matches(
                    rowMatch.Value,
                    CellPattern,
                    ExpressionOptions);
 
                for (int columnIndex = 0; columnIndex < cellMatches.Count; columnIndex++)
                {
                    dataRow[columnIndex] = cellMatches[columnIndex].Groups[1].ToString();
                }
 
                dataTable.Rows.Add(dataRow);
            }
        }
    }
 
    /// <summary>
    /// Given a string containing an HTML table, parse the header cells to create a set of DataColumns
    /// which define the columns in a DataTable.
    /// </summary>
    /// <param name="tableHtml">An HTML string containing a single HTML table</param>
    /// <returns>A set of DataColumns based on the HTML table header cells</returns>
    private static DataColumn[] ParseColumns(string tableHtml)
    {
        MatchCollection headerMatches = Regex.Matches(
            tableHtml,
            HeaderPattern,
            ExpressionOptions);
 
        return (from Match headerMatch in headerMatches
                select new DataColumn(headerMatch.Groups[1].ToString())).ToArray();
    }
 
    /// <summary>
    /// For tables which do not specify header cells we must generate DataColumns based on the number
    /// of cells in a row (we assume all rows have the same number of cells).
    /// </summary>
    /// <param name="rowMatches">A collection of all the rows in the HTML table we wish to generate columns for</param>
    /// <returns>A set of DataColumns based on the number of celss in the first row of the input HTML table</returns>
    private static DataColumn[] GenerateColumns(MatchCollection rowMatches)
    {
        int columnCount = Regex.Matches(
            rowMatches[0].ToString(),
            CellPattern,
            ExpressionOptions).Count;
 
        return (from index in Enumerable.Range(0, columnCount)
                select new DataColumn("Column " + Convert.ToString(index))).ToArray();
    }
}

/// <summary>
/// Tests for the HtmlTableParser class
/// </summary>
[TestClass]
public class ParserTest
{
    private TestContext testContextInstance;
 
    /// <summary>
    /// Verify that HtmlTableParser can parse an HTML file containing a single table. The
    /// test file includes a commented out table which should be ignored. Note some tags use
    /// attributes (we test we can parse tags with and without attributes).
    /// </summary>
    [TestMethod]
    [DeploymentItem(@"data\singleTable.txt")]
    public void TestParseSingleTable()
    {
        string html = File.ReadAllText("singleTable.txt");
        DataTable table = HtmlTableParser.ParseTable(html);
 
        AssertTable(GetExpectedData(), table);
    }
 
    /// <summary>
    /// Verify that HtmlTableParser can parse an HTML file containing multiple tables. The
    /// test file includes a commented out table which should be ignored. The test file
    /// contains tables both with and without headers.
    /// </summary>
    [TestMethod]
    [DeploymentItem(@"data\multipleTables.txt")]
    public void TestParseMultipleTables()
    {
        string html = File.ReadAllText("multipleTables.txt");
        DataSet dataSet = HtmlTableParser.ParseDataSet(html);
        Assert.AreEqual(3, dataSet.Tables.Count);
 
        var expected = GetExpectedData();
 
        foreach (DataTable table in dataSet.Tables)
        {
            AssertTable(expected, table);
        }
    }
 
    private static string[][] GetExpectedData()
    {
        return new[]
        {
            new[] { "row 1, cell 1", "row 1, cell 2" },
            new[] { "row 2, cell 1", "row 2, cell 2" }
        };
    }
 
    private static void AssertTable(string[][] expected, DataTable table)
    {
        Assert.AreEqual(expected.Count(), table.Rows.Count, "Table did not contain the expected number of rows");
 
        for (int i = 0; i < expected.Count(); i++)
        {
            for (int j = 0; j < expected[i].Count(); j++)
            {
                string actualElement = (table.Rows[i][j] as string).Trim();
                string expectedElement = expected[i][j];
 
                Assert.AreEqual<string>(expectedElement, actualElement, "Table did not contain the expected element");
            }
        }
    }
}

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
    <meta name="robots" content="all" />
      <title>Title</title>
</head>
 
<body>
      <!-- This table is commented out, so it shouldn't be parsed.
      <table border="1">
            <tr  border="1">
                  <th>Commented Heading 1</th>
                  <th>Commented Heading 2</th>
            </tr>
            <tr  border="1">
                  <td>Commented row 1, cell 1</td>
                  <td>Commented row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>Commented row 2, cell 1</td>
                  <td>Commented row 2, cell 2</td>
            </tr>
      </table>
      -->
 
      <!-- The parser should ignore the border attributes -->
      <table border="1">
            <tr  border="1">
                  <th>Heading 1</th>
                  <th>Heading 2</th>
            </tr>
            <tr>
                  <td border="1">row 1, cell 1</td>
                  <td>row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>row 2, cell 1</td>
                  <td>row 2, cell 2</td>
            </tr>
      </table> 
</body>
</html>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
    <meta name="robots" content="all" />
      <title>Title</title>
</head>
 
<body>
      <!-- The parser should ignore the border attributes -->
      <table border="1">
            <tr  border="1">
                  <td>row 1, cell 1</td>
                  <td>row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>row 2, cell 1</td>
                  <td>row 2, cell 2</td>
            </tr>
      </table> 
      <!-- This table is commented out, so it shouldn't be parsed.
      <table border="1">
            <tr  border="1">
                  <th>Commented Heading 1</th>
                  <th>Commented Heading 2</th>
            </tr>
            <tr  border="1">
                  <td>Commented row 1, cell 1</td>
                  <td>Commented row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>Commented row 2, cell 1</td>
                  <td>Commented row 2, cell 2</td>
            </tr>
      </table>
      -->
      <table border="1">
            <tr  border="1">
                  <th>Heading 1</th>
                  <th>Heading 2</th>
            </tr>
            <tr  border="1">
                  <td>row 1, cell 1</td>
                  <td>row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>row 2, cell 1</td>
                  <td>row 2, cell 2</td>
            </tr>
      </table> 
      <table>
            <tr>
                  <td>row 1, cell 1</td>
                  <td>row 1, cell 2</td>
            </tr>
            <tr  border="1">
                  <td>row 2, cell 1</td>
                  <td border="1">row 2, cell 2</td>
            </tr>
      </table> 
</body>
</html>

/// <summary>
/// A writer that provides a fast, non-cached, forward-only means of generating HTML streams.
/// </summary>
public class HtmlWriter : IDisposable
{
    public HtmlWriter(TextWriter writer)
    {
        this.Writer = writer;
        this.TagStack = new Stack<string>();
    }
 
    ~HtmlWriter()
    {
        Dispose(false);
    }
 
    private TextWriter Writer
    { 
        get; 
        set; 
    }
 
    private Stack<string> TagStack
    {
        get;
        set;
    }
 
    public static string MakeAnchor(string href, string text)
    {
        return string.Format("<a href=\"{0}\">{1}</a>", href, text);
    }
 
    public static string MakeAttribute(Attribute attribute)
    {
        return string.Format("{0}=\"{1}\"", attribute.Name, attribute.Value);
    }
 
    public static string MakeAttributeSet(Collection<Attribute> attributes)
    {
        StringBuilder attributeBuilder = new StringBuilder();
 
        foreach (Attribute attribute in attributes)
        {
            attributeBuilder.Append(" " + MakeAttribute(attribute));
        }
 
        return attributeBuilder.ToString();
    }
 
    public void WriteLine(string line)
    {
        // indent according to the tag stack depth
        if (this.TagStack.Count > 0)
        {
            line = new string('\t', this.TagStack.Count) + line;
        }
 
        this.Writer.WriteLine(line);
    }
 
    public void OpenTag(string tag)
    {
        this.WriteLine(string.Format("<{0}>", tag));
        this.TagStack.Push(tag);
    }
 
    public void OpenTag(string tag, Attribute attribute)
    {
        this.WriteLine(string.Format("<{0} {1}>", tag, MakeAttribute(attribute)));
        this.TagStack.Push(tag);
    }
 
    public void OpenTag(string tag, Collection<Attribute> attributes)
    {
        this.WriteLine(string.Format("<{0}{1}>", tag, MakeAttributeSet(attributes)));
        this.TagStack.Push(tag);
    }
 
    public void CloseTag(string tag)
    {
        if (this.TagStack.Count == 0)
        {
            throw new InvalidOperationException("Attempt to close HTML '" + tag + "' when there are no open tags.");
        }
 
        if (this.TagStack.Peek() != tag)
        {
            throw new InvalidOperationException("Attempt to close HTML '" + tag + "' when '" + this.TagStack.Peek() + "' is currently open.");
        }
 
        this.TagStack.Pop();
        this.WriteLine(string.Format("</{0}>", tag));
    }
 
    public void Tag(string tag, string content)
    {
        this.WriteLine(string.Format("<{0}>{1}</{0}>", tag, content));
    }
 
    public void Tag(string tag, Attribute attribute, string content)
    {
        this.WriteLine(string.Format("<{0} {1}>{2}</{0}>", tag, MakeAttribute(attribute), content));
    }
 
    public void Tag(string tag, Collection<Attribute> attributes, string content)
    {
        this.WriteLine(string.Format("<{0} {1}>{2}</{0}>", tag, MakeAttributeSet(attributes), content));
    }
 
    public void WriteStartDocument()
    {
        this.WriteLine("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.1 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml11-strict.dtd\">");
    }
 
    public void WriteMeta()
    {
        this.WriteLine("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=iso-8859-1\" />");
    }
 
    public void RefStylesheet(string stylesheet)
    {
        string tag = "<link rel=\"stylesheet\" href=\"{0}\" type=\"text/css\" media=\"screen\" />";
        this.WriteLine(string.Format(tag, stylesheet));
    }
 
    public void RefJavascript(string javascript)
    {
        string tag = "<script src=\"{0}\" type=\"text/javascript\"></script>";
        this.WriteLine(string.Format(tag, javascript));
    }
 
    #region IDisposable Members
 
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
 
    protected virtual void Dispose(bool disposing)
    {
        this.Writer.Dispose();
    }
 
    #endregion
}

/// <summary>
/// Html tag attribute as name value pair
/// </summary>
public struct Attribute
{
    public Attribute(string name, string value)
        : this()
    {
        Name = name;
        Value = value;
    }
 
    public string Name
    {
        get;
        private set;
    }
 
    public string Value
    {
        get;
        private set;
    }
}

public struct MyConvertible
{
    int value;
 
    public MyConvertible(int i)
    {
        value = i;
    }
 
    public static explicit operator MyConvertible(long l)
    {
        return new MyConvertible((int)l);
    }
 
    public static implicit operator long(MyConvertible c)
    {
        return c.value;
    }
 
    public override string ToString()
    {
        return this.value.ToString();
    }
}

class Contravariant
{
    public delegate void MyDelegate(Triangle value);
 
    void Example()
    {
        MyDelegate shapeDelegate = ShapeMethod;
        MyDelegate triangleDelegate = TriangleMethod;
 
        Triangle t = new Triangle();
        shapeDelegate(t);
    }
 
    public static void ShapeMethod(Shape value)
    {
    }
 
    public static void TriangleMethod(Triangle value)
    {
    }
}

public delegate void DelegateType();
 
public class DelegateHost
{
    public void InstanceMethod()
    {
        Console.WriteLine("Instance method."); 
    }
 
    public static void StaticMethod()
    {
        Console.WriteLine("Static method."); 
    }
}
 
public class Test
{
    private DelegateType delegateInstance;
 
    public void DoTest()
    {
        delegateInstance = new DelegateType(DelegateHost.StaticMethod);
        delegateInstance();
 
        DelegateHost host = new DelegateHost();
        delegateInstance = new DelegateType(host.InstanceMethod);
        delegateInstance();
    }
}

public class NiceClass
{
    private DependentClass injectedDependency;
 
    public NiceClass(DependentClass injectedDependency)
    {
        this.injectedDependency = injectedDependency;
    }
 
    public void CoupledMethod()
    {
        using (IFace c = new Face(injectedDependency))
        {
            // do something with c
        }
    }
}

public class NiceClass
{
    private DependentClass injectedDependency;
    private Func<DependentClass, IFace> faceFactoryMethod;
 
    public NiceClass(
        DependentClass injectedDependency, 
        Func<DependentClass, IFace> faceFactoryMethod)
    {
        this.injectedDependency = injectedDependency;
        this.faceFactoryMethod = faceFactoryMethod;
    }
 
    public void CoupledMethod()
    {
        using (IFace c = this.faceFactoryMethod(injectedDependency))
        {
            // do something with c
        }
    }
}

NiceClass nice = new NiceClass(dependency, d => new Face(d));