Windows Workflow allow us to perform custom validator input that is executed at design and compile time. The error output is similar as Biztalk Orchestration shape errors.
Adding a validator to a custom activity involves two steps:
- Create a class that derives from ActivityValidator class and override Validate method;
- Add a ActivityValidator attribute with the validator type to the custom activity;
As an example, i'm going to show a validator creation that verifies if a specific property is set.
I have already created a custom activity that is called Hello and have a property that receives the user name. To validate if the activity proprety is set, i'm going to create a validator.
ActivityValidator class creation:
As said early, to create a validator i have to create a class that derives from ActivityValidator. To perform the validation i have to override the validate method and set the validation code.
using System;
using
System.Text.RegularExpressions;
using
System.Workflow.ComponentModel.Compiler;
internal sealed class ExampleValidator : ActivityValidator {
public override ValidationErrorCollection Validate (ValidationManager manager, object obj)
{
if (manager == null throw new ArgumentNullException("Invalid manager.");)
if (obj == null throw new ArgumentNullException("Invalid activity.");)
HelloActivity activity = obj as HelloActivity
if (activity == null) throw new InvalidOperationException("Activity should be a HelloActivity.");
ValidationErrorCollection errors = base.Validate(manager, obj);
// Validate UserName property setting validationErrorCollection with information
// about the property that causes the error.
if (string.IsNullOrEmpty(activity.UserName)) {
errors.Add(ValidationError.GetNotSetValidationError("Username"));
}
return errors;
}
}
Custom activity and validator association
To associate the validator with the custom activity it's used the activityvalidator attribute.
[ActivityValidator(typeof(ExampleValidator))]
public sealed class HelloActivity : System.Workflow.ComponentModel.Activity {..
In the end the custom activity validator error will be show like this:
