serialize datatable to json

public string CreateJsonParameters(DataTable dt)
        {
            /* /****************************************************************************
             * Without goingin to the depth of the functioning of this Method, i will try to give an overview
             * As soon as this method gets a DataTable it starts to convert it into JSON String,
             * it takes each row and in each row it grabs the cell name and its data.
             * This kind of JSON is very usefull when developer have to have Column name of the .
             * Values Can be Access on clien in this way. OBJ.HEAD[0].<ColumnName>
             * NOTE: One negative point. by this method user will not be able to call any cell by its index.
             * *************************************************************************/
            StringBuilder JsonString = new StringBuilder();
            //Exception Handling        
            if (dt != null && dt.Rows.Count > 0)
            {
                JsonString.Append("{ ");
                JsonString.Append("\"Head\":[ ");
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    JsonString.Append("{ ");
                    for (int j = 0; j < dt.Columns.Count; j++)
                    {
                        if (j < dt.Columns.Count - 1)
                        {
                            JsonString.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":" + "\"" + dt.Rows[i][j].ToString() + "\",");
                        }
                        else if (j == dt.Columns.Count - 1)
                        {
                            JsonString.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":" + "\"" + dt.Rows[i][j].ToString() + "\"");
                        }
                    }
                    /*end Of String*/
                    if (i == dt.Rows.Count - 1)
                    {
                        JsonString.Append("} ");
                    }
                    else
                    {
                        JsonString.Append("}, ");
                    }
                }
                JsonString.Append("]}");
                return JsonString.ToString();
            }
            else
            {
                return null;
            }
        }