Lists, Arrays and collections within BizTalk orchestrations

> > **Update 2012-03-28** Unfortunately the images for this post was lost in upgrade of the blog. > >

This post shows how it’s possible to create your own .NET class and then use this within your orchestration (as a variable) to work with typed lists - something that unfortunately isn’t supported out of the box in BizTalk orchestrations. Below is the class used to create a typed list for System.String objects.

<span class="kwrd">using</span> System;
<span class="kwrd">using</span> System.Collections.Generic;
<span class="kwrd">using</span> System.Text;

<span class="kwrd">namespace</span> Sample.BizTalkCollections
{
    [Serializable]
    <span class="kwrd">public</span> <span class="kwrd">class</span> StringList
    {
        <span class="kwrd">private</span> List<<span class="kwrd">string</span>> _list = <span class="kwrd">new</span> List<<span class="kwrd">string</span>>();

        <span class="kwrd">public</span> <span class="kwrd">void</span> Add(<span class="kwrd">string</span> item)
        {
            _list.Add(item);
        }

        <span class="kwrd">public</span> <span class="kwrd">int</span> Count()
        {
            <span class="kwrd">return</span> _list.Count;
        }

        <span class="kwrd">public</span> <span class="kwrd">bool</span> Remove(<span class="kwrd">string</span> item)
        {
            <span class="kwrd">return</span> _list.Remove(item);
        }

        <span class="kwrd">public</span> <span class="kwrd">void</span> RemoveAt(<span class="kwrd">int</span> index)
        {
            _list.RemoveAt(index);
        }

        <span class="kwrd">public</span> <span class="kwrd">override</span> <span class="kwrd">string</span> ToString()
        {
            StringBuilder builder = <span class="kwrd">new</span> StringBuilder();
            <span class="kwrd">foreach</span> (<span class="kwrd">string</span> item <span class="kwrd">in</span> _list)
            {
                builder.AppendLine(item);
            }

            <span class="kwrd">return</span> builder.ToString();
        }
    }
}

Notice that the class is serializable so BizTalk can serialize when dehydrating the orchestration to the database. We’ve also chosen not to extend the IList interface as we don’t want to expose all methods of that interface, but only the once we’ll really going use within our orchestrations.

This StringList class exists within the BizTalkCollections namespace where we have other classes for lists types with different datatypes (for example ObjectList, Int32List and so on). Below is a picture showing the structure of the Visual Studio project containing all the collections we current have implemented. This project and the BizTalk testproject is available for download here.

In the orchestration we then have set up a variable and type this to our StringList class within the Sample.BizTalkCollections namespace.

Also make sure the assembly with your collection class is installed in the GAC, otherwise you’ll end up with a _FileNotFound exception _saying

> > Could not load file or assembly 'Sample.BizTalkCollections, Version=1.0.0.0, Culture=neutral, PublicKeyToken=7109528d5dbf986b' or one of its dependencies. The system cannot find the file specified. > >

Then you can use the following code within your orchestration! Download the sample project and test it.

A really generic class

I’d really like for it be possible to create my own generic classes and then initialize these using something like the below.

genericList = Sample.BizTalkCollections.GenericList<System.String>();

However this isn’t possible as BizTalk orchestrations don’t seem to understand generic classes … If someone found a solution to this please let me/us know via the comments to this post.