DataTable to JSON string

var lst = dt.AsEnumerable()
    .Select(r => r.Table.Columns.Cast<DataColumn>()
            .Select(c => new KeyValuePair<string, object>(c.ColumnName, r[c.Ordinal])
           ).ToDictionary(z=>z.Key,z=>z.Value)
    ).ToList();

var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
return serializer.Serialize(lst);