Simple class to create csv
Before you do other things you should separate and encapsulate, this means you should put certain logic into their own methods that specialize in doing only one thing. If you put e.g. the loops in such method methods, you won't need any comments. Here's an example of how it could be done with C# 7. Also notice the changed names. There's no need for the a/an/the prefixes.

This is just a start and there is much more to improve. I left it out intentionally.

public void CreateCsv(DataTable data, string path, string title)
{
    string CreateFileName() =&gt; string.Concat(path, title, @"-", guid, @".csv");

    void WriteHeader(StringBuilder csv)
    {
        var header = new List&lt;string&gt;();
        foreach (var column in data.Columns.Cast&lt;DataColumn&gt;())
        {
            header.Add(column .ColumnName);
        }
        csv.AppendLine(string.Join(Delimiter, header));
    }

    void WriteData(StringBuilder csv)
    {
        foreach (var row in data.Rows.Cast&lt;DataRow&gt;())
        {
            var values = new List&lt;string&gt;();
            foreach (var column in data.Columns.Cast&lt;DataColumn&gt;())
            {
                values.Add(row[column.ColumnName].ToString());
            }
            csv.AppendLine(string.Join(Delimiter, values));
        }
    }

    string WriteCsv() 
    {
        var csv = new StringBuilder();  
        WriteHeader(csv);
        WriteData(csv);
        return csv.ToString();
    }           

    File.WriteAllText(CreateFileName(), WriteCsv());

    Console.WriteLine();
    Console.WriteLine(String.Concat(@"just completed: ", title, @"-", this.guid, @".csv"));
}