C# DataTable转json

public static string jsonForEasyui(string totalCount, DataTable dt)
        {
            StringBuilder builder = new StringBuilder();
            builder.Append("{ ");
            builder.Append("\"total\":\"" + totalCount + "\",");
            builder.Append("\"rows\":[ ");
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                builder.Append("{ ");
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    if (j < (dt.Columns.Count - 1))
                    {
                        builder.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":" + "\"" + ReplaceBadChar(dt.Rows[i][j].ToString()) + "\",");
                    }
                    else if (j == (dt.Columns.Count - 1))
                    {
                        builder.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":" + "\"" + ReplaceBadChar(dt.Rows[i][j].ToString()) + "\"");
                    }
                }
                if (i == (dt.Rows.Count - 1))
                {
                    builder.Append("} ");
                }
                else
                {
                    builder.Append("}, ");
                }
            }
            builder.Append("]}");
            return builder.ToString();
        }