This is my simple code for inserting data to database and it’s working fine. Table name is AccountMaster

function Insert() {
    var Value = {};
    Value.Id = $("[id*=hdnId]").val();
    Value.AccountName = $("[id*=txtAccountName]").val();
    Value.Catagory = $("[id*=txtCatagory]").val();
    Value.CatagorySr = $("[id*=hdnCatagorySr]").val();
    Value.HeadName = $("[id*=hdnHeadName]").val();
    Value.HeadId = $("[id*=hdnHeadId]").val();
    Value.BalanceSheetSr = $("[id*=hdnBalanceSheetSr]").val();
    Value.AccountTypeName = $("[id*=txtAccountTypeName]").val();
    Value.AccountTypeId = $("[id*=hdnAccountTypeId]").val();
    Value.AccountTypeSr = $("[id*=hdnAccountTypeSr]").val();
    Value.Sr = $("[id*=txtSr]").val();
    Value.AccountCode = $("[id*=hdnAccountCode]").val();
    Value.OpeningBalance = $("[id*=txtOpeningBalance]").val();
    Value.Nature = $("[id*=ddlNature]").val();
    Value.ClosingBalance = $("[id*=txtClosingBalance]").val();
    Value.PrevYearIE = $("[id*=txtPrevYearIE]").val();
    Value.TINNo = $("[id*=txtTINNo]").val();
    Value.GSTNo = $("[id*=txtGSTNo]").val();
    Value.Remark = $("[id*=txtRemark]").val();
    Value.Address = $("[id*=txtAddress]").val();
    Value.EntryBy = '<%=Session["Name"]%>';
    Value.ChangedBy = '<%=Session["Name"]%>';
    $.ajax({
        type: "POST",
        url: "AccountMaster.aspx/InsertUpdate",
        data: '{Value: ' + JSON.stringify(Value) + '}',
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (response) {
            alert("Saved Successfully");
        },
        error: function (xhr, status, error) {
            alert(xhr.responseText);
        }
    });
}

Above code shows that every time I have to add fields to Value one by one. If I have more than 100 fields in a database table I have to add it one by one which is very painful sometimes.
So I decided to parameterize that section by collecting all the fields from database table and add them through loop like this…

function Insert(FormName, DivName) {
    $.ajax({
        type: "POST",
        url: "" + FormName + ".aspx/GetData",
        data: '{}',
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (response) {
            var xmlDoc = $.parseXML(response.d);
            var xml = $(xmlDoc);
            var Records = xml.find("Table");
            if (Records.length > 0) {
                var Main = {};
                $.each(Records, function () {
                    var record = $(this);
                    var ColName = record.find("Column_name").text();   //Getting Column names from database
                    var ColValue = GetColumnsValue(ColName, DivName);  // getting columns value in webform.
                    Main.ColName = ColValue; // adding columns value to Main, this line is not working                     
                });
                $.ajax({
                    type: "POST",
                    url: "" + FormName + ".aspx/Insert",
                    data: "{MainValues: " + JSON.stringify(Main) + "}",
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (response) {

                    },
                    error: function (xhr, status, error) {
                        alert(xhr.responseText);
                    }
                }).done(function () {
                });
            }
        },
        error: function (d) {
            alert(d.responseText);
        }
    });
}

As usual above method thinks ColName is the field of database table.
And here is my GetData code in c#

[WebMethod]
        public static string GetData()
        {
            using (SqlCommand Cmd = new SqlCommand())
            {
                using (SqlConnection Con = Connections.Create())
                {
                    Cmd.Connection = Con;
                    Cmd.CommandText = "GetColumnList_pro".Trim();
                    Cmd.CommandType = CommandType.StoredProcedure;
                    Cmd.Parameters.AddWithValue("Option", "GetColumnList".Trim());
                    Cmd.Parameters.AddWithValue("Table", "DummyTable".Trim());
                    using (SqlDataAdapter Adp = new SqlDataAdapter())
                    {
                        using (DataSet Ds = new DataSet())
                        {
                            Con.Open();
                            Adp.SelectCommand = Cmd;
                            Adp.Fill(Ds);
                            return Ds.Geml();
                        }
                    }
                }
            }
        }