Convert VB.NET Code to C#

Question

How to convert this VB.NET code to C#. 
Private Function ConvertHTMLTablesToDataSet(ByVal HTML As String) As DataSet
        ' Declarations  
        Dim ds As New DataSet
        Dim dt As DataTable
        Dim dr As DataRow
        Dim dc As DataColumn
        Dim TableExpression As String = "<table[^>]*>(.*?)</table>"
        Dim HeaderExpression As String = "<th[^>]*>(.*?)</th>"
        Dim RowExpression As String = "<tr[^>]*>(.*?)</tr>"
        Dim ColumnExpression As String = "<td[^>]*>(.*?)</td>"
        Dim HeadersExist As Boolean = False
        Dim iCurrentColumn As Integer = 0
        Dim iCurrentRow As Integer = 0

        ' Get a match for all the tables in the HTML  
        Dim Tables As MatchCollection = Regex.Matches(HTML, TableExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase)

        ' Loop through each table element  
        For Each Table As Match In Tables

            ' Reset the current row counter and the header flag  
            iCurrentRow = 0
            HeadersExist = False

            ' Add a new table to the DataSet  
            dt = New DataTable

            ' Create the relevant amount of columns for this table (use the headers if they exist, otherwise use default names)  
            If Table.Value.Contains("<th") Then
                ' Set the HeadersExist flag  
                HeadersExist = True

                ' Get a match for all the rows in the table  
                Dim Headers As MatchCollection = Regex.Matches(Table.Value, HeaderExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase)

                ' Loop through each header element  
                For Each Header As Match In Headers
                    dt.Columns.Add(Header.Groups(1).ToString)
                Next
            Else
                For iColumns As Integer = 1 To Regex.Matches(Regex.Matches(Regex.Matches(Table.Value, TableExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase).Item(0).ToString, RowExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase).Item(0).ToString, ColumnExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase).Count
                    dt.Columns.Add("Column " & iColumns)
                Next
            End If

            ' Get a match for all the rows in the table  
            Dim Rows As MatchCollection = Regex.Matches(Table.Value, RowExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase)

            ' Loop through each row element  
            For Each Row As Match In Rows

                ' Only loop through the row if it isn't a header row  
                If Not (iCurrentRow = 0 And HeadersExist = True) Then

                    ' Create a new row and reset the current column counter  
                    dr = dt.NewRow
                    iCurrentColumn = 0

                    ' Get a match for all the columns in the row  
                    Dim Columns As MatchCollection = Regex.Matches(Row.Value, ColumnExpression, RegexOptions.Multiline Or RegexOptions.Singleline Or RegexOptions.IgnoreCase)

                    ' Loop through each column element  
                    For Each Column As Match In Columns

                        ' Add the value to the DataRow  
                        dr(iCurrentColumn) = Column.Groups(1).ToString

                        ' Increase the current column   
                        iCurrentColumn += 1
                    Next

                    ' Add the DataRow to the DataTable  
                    dt.Rows.Add(dr)

                End If

                ' Increase the current row counter  
                iCurrentRow += 1
            Next

            ' Add the DataTable to the DataSet  
            ds.Tables.Add(dt)

        Next

        Return ds

    End Function