MEF has now been released, a Plug-In Framework, for .Net 4.0

After reading up on CodePlex, I have generated a small application that provides a plug-in framework, see attached below.

http://mef.codeplex.com/wikipage?title=Guide&referringTitle=Overview

MEF.zip (70.88 kb)

I’ve also produced a .NET 3.5 version too:

MEF in 3.5.zip (427.41 kb)

Few MEF links:

Glenn Block

Nicholas Blumhardt

MEF on CodePlex

Channel 9 Silverlight 4 MEF Screencasts

MEF 101

The use of DataAnnotations, has increased over the years, as many frameworks are using it more and more, (MVC, Silverlight, etc).

However if you need to perform validation within your application and it is not any known framework then can we still use DataAnnotations?

The answer is yes, I’ll try and take you through how you can go about it.

First lets create a class that we are going to use:

    public class Contact
    {

        [Required]
        [RegularExpression(@”\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*([,;]\s*\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*)*”, ErrorMessage = “Invalid email address”)]
        public string Email { get; set; }

        [Required]
        [StringLength(20)]
        public string FirstName { get; set; }

        [Required]
        public string LastName { get; set; }

        [Range(10,30)]
        public int Age {get;set;}

        public string City { get; set; }   

    }

All of these validations are standard and out of the box when using DataAnnotations.

Next we need to be able to hold the Error Information, so I’ve created a class called ErrorInfo

    public class ErrorInfo
    {
        public ErrorInfo(string propertyName, string errorMessage, object instance)
        {
            PropertyName = propertyName;
            ErrorMessage = errorMessage;
            Instance = instance;
        }

        public string PropertyName { get; set; }
        public string ErrorMessage { get; set; }
        public object Instance { get; set; }

    }

Now the clever bit, the Validation Runner (this was kindly supplied by Steve Sanderson and his xVal)

 

    internal static class DataAnnotationsValidationRunner
    {
        public static IEnumerable<ErrorInfo> GetErrors(object instance)
        {
            return from prop in TypeDescriptor.GetProperties(instance).Cast<PropertyDescriptor>()
                   from attribute in prop.Attributes.OfType<ValidationAttribute>()
                   where !attribute.IsValid(prop.GetValue(instance))
                   select new ErrorInfo(prop.Name, attribute.FormatErrorMessage(string.Empty), instance);
        }
    }

So that is the hard work done, now lets check for validation:

     IEnumerable<ErrorInfo> errors = DataAnnotationsValidationRunner.GetErrors(contact);

How easy is that?

Okay now lets pick things up, What I would like to do next is Validate the City, to be a city in the UK, something like this would be nice:

      [City(ValidCity=”Gloucester”)]
      public string City { get; set; }

In order to do this you are going to have to generate your own Attribute which needs to be based on the ValidationAttribute, again this is quite simple

 

    public class CityAttribute : ValidationAttribute
    {
        public string ValidCity { get; set; }

        public override bool IsValid(object value)
        {
            if (value == null)
            {
                return true;
            }

            if (value.ToString() != ValidCity)
            {
                return false;
            }

            return true;
        }
    }

 

So you now can generate your own custom validation attributes with your own business rules.

DataAnnotationsValidation.zip (11.78 kb)

From time to time I need to generate Sequence Diagrams, as this are required to graphically represent processes, as a consultant each customer has a different sent of tools you can and can not use.  So it becomes hard to generate what should be something you don’t have to think about.

I found a great on-line tool Web Sequence Diagrams, it so simple and it also has a very easy to use API.

Just to show you how easy here is what I generated in what must have been 5 minutes

It can also be support in plain HTML, as you can see in the attached file

Commit Sequence.htm (457.00 bytes)

 

The time has come where I needed to handle streams, so the first I needed to generate some tests and within these tests I need to generate a stream based on some text.  So the first task was to convert a String in to a Stream, and while I am at it how about the other direction to (Stream to a String)

String in to a Stream

string text = “To Jani, Reminder Don’t forget me this weekend!'”;
byte[] byteArray = Encoding.ASCII.GetBytes(text);
MemoryStream streamXML = new MemoryStream(byteArray);

Stream to a String

xml.Seek(0, SeekOrigin.Begin);
var readerXML = new StreamReader(xml);
string textXML = readerXML.ReadToEnd();