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PaginationHelper

The PaginationHelper simplify the creation of paginated navigation on items.

Example

Suppose you have a set with 400 items:

public class MyController : SmartDispatcherController
{
    public void List()
    {
        PropertyBag["items"] = ObtainMyLargeCollection();
    }

    private IList ObtainMyLargeCollection()
    {
        ...
    }
}

With the PaginationHelper you can return a sliced representation of the collection:

public class MyController : SmartDispatcherController
{
    public void List()
    {
        PropertyBag["items"] = PaginationHelper.CreatePagination( ObtainMyLargeCollection(), 10 );
    }

    private IList ObtainMyLargeCollection()
    {
        ...
    }
}

The help will look for a page on Request.Params to define its starting index. The CreatePagination method returns a IPaginatedPage object which exposes several properties so you can build a nice pagination box:

• CurrentPageIndex
• PreviousPageIndex
• NextPageIndex
• FirstItemIndex
• LastItemIndex
• TotalItems
• PageSize
• HasPreviousPage
• HasNextPage
• HasPage
• TotalPages
• CurrentPageSize
• FirstItem
• LastItem

NVelocity example

This a snippet that renders the items and the pagination box:

#foreach($row in $items)
  <tr>
    <td>$row.Name</td>
    <td>$row.Email</td>
  </tr>
#end</table>

<div class="pagination">
<table width="100%" border="0">
  <tr>
  <td>Showing $items.FirstItemIndex - $items.LastItemIndex of $items.TotalItems</td>
  <td align="right">
#if($items.HasPreviousPage) $PaginationHelper.CreatePageLink( 1, "first" ) #end
#if(!$items.HasPreviousPage) first #end
#if($items.HasPreviousPage) | $PaginationHelper.CreatePageLink( $items.PreviousPageIndex, "prev" ) #end
#if(!$items.HasPreviousPage) | prev #end
#if($items.HasNextPage) | $PaginationHelper.CreatePageLink( $items.NextPageIndex, "next" ) #end
#if(!$items.HasNextPage) | next #end
#if($items.HasNextPage) | $PaginationHelper.CreatePageLink( $items.TotalPages, "last" ) #end
#if(!$items.HasNextPage) | last #end
  </td>
  </tr>
</table>
</div>

This will result in something like the following

Cached Pagination

The PaginationHelper has a cached version of its functionality. That allows the data source to be loaded and reused for a limited period of time. The cachekey must be carefully defined with the application semantics in mind. A bad cachekey might allow the data source to be shared by request from different users and with different data source search criterias (when the data source is the result of a search)

Suppose you have a form with many search criterias:

Your view will look something similar to this, and make sure to POST rather than GET:

<form id="search" method="post" action="$siteRoot/Cars/Search.aspx"
&lt;input id="make" type="text" size="14" name="make" /><br />
<input id="model" type="text" size="14" name="model" /><br />
<input id="year" type="text" size="14" name="year" /><br />
<input type="Submit" class="button" value="Search!" />

The pagination helper exposes a delegate that you will need to grab your search results. Pass it your method that handles the actual searching. Here is an example controller:

public class CarController : SmartDispatcherController
{
    private String make, model, year;
    
    public IList PerformSearch()
    {
        // Do your actual search
        
        return Car.FindByMakeModelYear(make, model, year);
    }
    
    public void Search(String make, String model, String year)
    {
        // create the pagination
        
        PropertyBag["Cars"] = PaginationHelper.CreateCachedPagination(
            "carssearchkey" + this.make + this.model + this.year, 
            5, new     DataObtentionDelegate(PerformSearch));
    }
}

Our resulting view, it is important that we expose our criteria to the view so the next/first/last/prev links can be correctly constructed and work properly:

<table cellpadding="4">
    <tr>
        <th>Make</th>
        <th>Model</th>
        <th>Year</th>
    </tr>
#foreach($Car in $Cars)
    <tr>
        <td>$!Car.Make</td>
        <td>$!Car.Model</td>
        <td>$!Car.Year</td>
    </tr>
#end
</table>
<div class="pagination" id="pagination">
<table width="90%" border="0">
    <tr>
        <td>Showing $Cars.FirstItemIndex - $Cars.LastItemIndex of $Cars.TotalItems</td>
        <td align="right">
        #if($Cars.HasPreviousPage) 
            $PaginationHelper.CreatePageLink( 1, "first",null, "%{make=$make, model=$model,year=$year}" ) 
        #else
            first
        #end
        #if($Cars.HasPreviousPage) 
            | $PaginationHelper.CreatePageLink( $Cars.PreviousPageIndex, "prev",null, "%{make=$make,model=$model,year=$year}" ) 
        #else
            | prev 
        #end
        #if($Cars.HasNextPage) 
            | $PaginationHelper.CreatePageLink( $Cars.NextPageIndex, "next",null, "%{make=$make,model=$model,year=$year}" ) 
        #else
            | next
        #end
        #if($Cars.HasNextPagePage) 
            | $PaginationHelper.CreatePageLink( $Cars.TotalPages, "last",null, "%{make=$make,model=$model,year=$year}" ) 
        #else
            | last
        #end
        </td>
    </tr>
</table>
</div> <!-- end pagination -->

And how it looks:

API documentation

You may also consult the API documentation for the PaginationHelper.

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