When you create a new Workflow Studio activity project within Visual Studio, the templates provide you with a pretty comprehensive and documented activity class file. In the screen shot below, I minimized a lot of the code, but you can see the primary sections of the activity file within the project.
The primary sections of this file are listed below:
- Using statements
- General activity properties
- Class constructor
- Standard properties
- Dependency properties
- Activity execution section
- Property validation section
In this blog, I’ll discuss at a high level each of these primary sections. I won’t detail the meaning of all of the attributes and properties that are present as they are pretty well documented within the Activity Developers Guide and within the comments of the class file itself. This blog is really meant to give you an overview of what is actually in here so you can navigate to the appropriate section as you develop your activity.
1. Using statements:
There is a long list of using statements at the top that define the references for the class. What you should notice here is that the last five all come from Workflow Studio. If your activity references a third party DLL, you’ll most likely need to add more using statements to make sure your references are all in place.
2. General activity properties:
Right beneath the using statements is a section called “Attribute Definitions and Comments”. This section contains a series of general properties for the activity. The comments provided within this section explain these settings pretty well. A few of them you should take note of are below.
This is the name of the activity displayed within the Workflow Studio Designer.
[Description(@”This activity will delay for a specified amount of time”)]
This is the description of the activity displayed within the Workflow Studio Designer. When you select the activity in the Activity pane, the description is shown in the lower-left corner of the Designer.
This is the folder location for where the activity is placed within the Activity pane of the Workflow Studio Designer. A forward slash is used to specify a subfolder.
3. Class constructor:
The class constructor is next. This code gets executed when the activity is placed on the drag-and-drop surface within the Designer. The most common thing you’ll need to do in the constructor is to initialize the values of your properties.
4. Standard properties:
The section for standard properties is listed after the class constructor. A sample one is provided in the template which is commented out. This sample is mainly here to give you the syntax for defining a sample property if you would like to use one within your code.
What you really need to know is that there are two types of properties you can define within the class – standard properties and dependency properties. The primary difference between them is that dependency properties are “bindable” to other activities whereas standard properties cannot be bound. Dependency properties have much more flexibility than standard properties due to being bindable. In the Designer, bindable properties allow their values to come from other activities. Bindable properties can also be used as input to properties of other activities. Due to this flexibility, dependency properties are much more common to use than standard properties and you should probably define all of your properties as dependency properties first, then fall back to being standard if the bindable behavior is not desired.
5. Dependency properties:
The dependency property section is listed after the standard property section. As stated in the section above, dependency properties are much more common to use than standard properties since they can be bound to the properties of other activities. Their flexibility makes them a much better choice in most cases.
The activity template gives you a series of sample dependency properties that are commented out. I won’t go into all of the code for this property here (it’s explained pretty well within the Activity Developers Guide). I’ll just highlight a portion of the settings here…
This is the default value of the property. Default values can also be set within the class constructor. When using the Workflow Studio Designer, if the property value is ever set to something different than this default value, the value is shown as bold within the Designer to indicate it has changed.
This is the name of the property as shown within the Workflow Studio Designer. This name should be intuitive and easy for admins to understand.
[Description(@”Amount of time to sleep in ms”)]
This is the description of the property as shown within the Workflow Studio Designer. When you select the property in the Designer, this text is shown in the lower-right corner of the Designer.
This setting defines whether this property is visible within the Workflow Studio Designer. If set to true, it is displayed within the Designer when the activity is selected. If you don’t want admins to know about this property or see it within the Designer, you can set browsable to false.
A property can either be an input property or output property. Input properties define some value that is inputted into the activity. Output properties define something that is returned by the activity after the activity is executed. The use of the [InputAttribute] or [OutputAttribute] declaratation defines what icons should be used for this property in the Workflow Studio Designer.
6. Activity execution section:
After all of the properties are defined, the next section is the Execute() function. This function gets called when the activity is executed by Workflow Studio. All of the execution logic should go into this function.
The Execute() function provides a try/catch block. Put all of your execution logic in the try block. Don’t touch the ExpandStringProperties() call at the top as this function will dynamically retrieve the property values set within the Workflow Studio Designer at runtime so that you can use them within the try block.
7. Property validation section:
The last section of the file defines how property validation is performed within the Workflow Studio Designer. If you have used the out-of-the-box activities within the Designer, you may have noticed that some activities have required properties that need to be set in order for them to be valid. These properties provide a red X or yellow warning icon to inform admins that they are required or desired to be set. You can set up the same type of functionality for your properties through the code in this section. There are a lot of comments within this section to explain how to set up your properties for validation, so I won’t go into this here. I may blog about this in the future as it could be a big discussion on its own.
Blogs in this series:
- Getting Started
- Setting up your Visual Studio development environment
- Anatomy of a Workflow Studio activity project (this one)
- Testing your Workflow Studio activity project
- [Stepping through your Workflow Studio activity project code]