Developer's Log: C#

Here is a complete example and walkthrough for dynamically cloning a container that has a set of HTML controls.

I used jquery for scripting, so included the library reference in the head section.

<head>

   <script type="text/javascript" src="js/jquery-1.7.1.min.js"></script>

</head>

As for the body, let's add a button to open up our modal dialog.

<body>

...

<div id="calc-se-buttons">
    <input type="button" value="Print" id="print" name="print" class="button" />
</div>

Let's now create a container that has the contents that we intend to clone. In this example, we will clone the container with the id print-input, . Assigning a style (print-input-style) to the container which we want to clone is important here, because later we will depend on style name while calculating the number of cloned elements that we currently have.

<div id="print">
    <br/>
    <div id="print-input-1" class="print-input-style" >
        <label for="modal-print-title-1">Title</label>&nbsp;
        <select name="modal-print-title-1" id="modal-print-title-1">
                <option value='Mr'>Mr</option>
                <option value='Miss'>Miss</option>
                <option value='Ms'>Ms</option>
                <option value='Mrs'>Mrs</option>
                <option value='Dr'>Dr</option>
                <option value='Fr'>Fr</option>
            </select>&nbsp;&nbsp;
        <label for="modal-print-name-1">First Name</label>&nbsp;
        <input name="modal-print-name-1" id="modal-print-name-1" type="text" size="6" />&nbsp;&nbsp;
        <label for="modal-print-surname-1">Last Name</label>&nbsp;
        <input name="modal-print-surname-1" id="modal-print-surname-1" type="text" size="6" />
        <br/>
    </div>
    <br/><br/>
    <div id="div-add-customer">
        <img id="add-customer" src="../images/add-more.gif" alt="Add New Customer" width="20" height="20" />
    </div>
</div>

Next, let's implement the jquery function that clones the print-input container and bind it to the add-customer button.

This function simply counts the current number of clonable elements, clones one of them and assigns an incremented number for each of the element ids. So, as new elements are added, main container ids go one after the other like print-input-1, print-input-2,.... The ids of the contained controls are also incremented accordingly.

There is a business rule to limit the number of added elements to 4. This is quite useful if you want to keep the size of your container consistent or limit the number of elements for some reason.

$(document).ready(function () {
  $('#add-customer').click(function () {

    // how many "duplicatable" input fields we currently have
    var num = $('.print-input-style').length;

    // the numeric ID of the new input field being added 
    var newNum = new Number(num + 1);

    var currentContainerId = '#print-input-' + num;
 
    // create the new element via clone(), and manipulate it's ID using newNum
    var newElem = $(currentContainerId).clone().attr('id', 'print-input-' + newNum);
 
    // manipulate the name/id values of the input inside the new element
    $(currentContainerId).children('label').each(function (i) {
      var attrFor = $(this).attr('for');
      $(this).attr('for', attrFor.substring(0, attrFor.lastIndexOf("-") + 1) + newNum);

    });
    $(currentContainerId).children('select').each(function (i) {
      var attrId = $(this).attr('id');
      var attrName = $(this).attr('name');
      $(this).attr('id', attrId.substring(0, attrId.lastIndexOf("-") + 1) + newNum)
        .attr('name', attrName.substring(0, attrName.lastIndexOf("-") + 1) + newNum);
    });
    $(currentContainerId).children('input').each(function (i) {
      var attrId = $(this).attr('id');
      var attrName = $(this).attr('name');
      $(this).attr('id', attrId.substring(0, attrId.lastIndexOf("-") + 1) + newNum)
        .attr('name', attrName.substring(0, attrName.lastIndexOf("-") + 1) + newNum);
    });
 
    // insert the new element after the last "duplicatable" input field
    $(currentContainerId).after(newElem);
 
    // business rule: you can only add 4 names

    if (newNum == 4)
      $('#add-customer').attr('disabled', 'disabled');
    });
});

There, each time you hit the plus button (add-customer), the entire row is duplicated.

Working on repayment frequency enumeration and its annual occurence, I came up with the idea of implementing field attributes. Then found a good way to obtain the value of annual occurences which is embedded to the attribute. I implemented an enumeration extension to achieve this.

This is a neat and tidy way to enrich enumerations with custom attributes and get the values of these attributes by an enumeration extension.

The enumeration class:

namespace MyApplication.Domain.Enumerations

{

public enum RepaymentFrequency

{

[AnnualOccurence(12)]

[DaysImplied(30)]

Monthly,

[AnnualOccurence(52)]

[DaysImplied(7)]

Weekly,

....
....
}

The custom attribute class for AnnualOccurence (it will be pretty much the same for DaysImplied):

using System;
 
namespace MyApplication.Domain.Enumerations
{
    [AttributeUsage(AttributeTargets.Field)]
    public class AnnualOccurence : Attribute
    {
        public static readonly short Unassigned = -1;
 
        public AnnualOccurence()
        {
            _numberOfAnnualRepayments = Unassigned;
        }
 
        private short _numberOfAnnualRepayments;
        public short NumberOfAnnualRepayments
        {
            get { return _numberOfAnnualRepayments;}
        }
 
        public AnnualOccurence(short numberOfOccurences)
        {
            _numberOfAnnualRepayments = numberOfOccurences;
        }
 
        public override string ToString()
        {
            return "Annual Occurence = " + _numberOfAnnualRepayments.ToString();
        }
    }
}

Now, there is a good way to get the values of such attributes from an 'enumeration instance', by implementing the following extension:

using System;
using System.Linq;
 
namespace HomeStart.LoanCalculators.Domain.Enumerations
{
    public static class EnumExtensions
    {
        public static Expected GetAttributeValue<T, Expected>

                      (this Enum enumeration, Func<T, Expected> expression)
            where T : Attribute
        {

         T attribute = enumeration.GetType().GetMember(enumeration.ToString())[0]

                            .GetCustomAttributes(typeof(T), false)

                               .Cast<T>().SingleOrDefault();
 
            if (attribute == null)
                return default(Expected);
 
            return expression(attribute);
        }
    }
}

with the following usage:

 
RepaymentFrequency repaymentFrequency = repaymentFrequency.Weekly;

...

var numberOfAnnualRepayments =

                 repaymentFrequency.GetAttributeValue<AnnualOccurence, short>

                                            (x => x.NumberOfAnnualRepayments);

var numberOfDaysImplied =

                 repaymentFrequency.GetAttributeValue<DaysImplied, short>

                                            (x => x.NumberOfDaysImplied);

...

where 52 will be assigned to numberOfAnnualRepayments,

and 7 will be assigned to numberOfDaysImplied in this case.

Developer's Log

Saturday, 17 March 2012

DYNAMICALLY CLONING HTML CONTROLS USING JQUERY

Saturday, 4 February 2012

ENRICH ENUMS WITH ATTRIBUTES AND RETRIEVE VALUES GENERICALLY