Transactional NTFS (part 1/2)

.NET C#

Transactional NTFS and DotNet

Starting from Windows Vista and Windows Server 2008, Microsoft introduced a great new feature called Transactional NTFS (TxF).

It allows developers to write file I/O functions that are guaranteed to either succeed completely or fail completely.
Unfortunately there are no classes in the .NET framework that would allows us to perform, such operations.
We need to resort to P/Invoke to use the newly introduced functions CreateTransaction, CommitTransaction, RollbackTransaction and DeleteFileTransacted. Continue reading →

How we do ASP.NET MVC

.NET ASP.NET MVC

Sample MVC Solution

In this post I will show a sample ASP.NET MVC 2.0 project structure illustrating different concepts such as data access, user input validation and mapping between the domain and the view model. The project is still under construction but the source code is available at github.

I will illustrate the usage of the following frameworks:

MvcContrib bringing useful extension methods and strongly typed helpers to ASP.NET MVC
AutoMapper enabling easy mapping between the domain and the view models
FluentValidation – a small validation library for .NET that uses a fluent interface and lambda expressions for building validation rules for your business objects
NHibernate – a popular ORM in the .NET world
FluentNHibernate – a statically compiled alternative to NHibernate’s standard hbm xml mapping
Spring.NET – object container and dependency Injection framework for .NET
Rhino.Mocks – A dynamic mock object framework for the .Net platform. It’s purpose is to ease testing by allowing the developer to create mock implementations of custom objects and verify the interactions using unit testing

Armed with this arsenal of frameworks let’s start exploring the solution structure. I’ve opted for 2 projects solution but in many real world applications more levels of abstraction could be brought to the business layer. Personally I favor to have less big assemblies rather than many small assemblies into the solution. Fewer the assemblies, faster the load time and faster the IDE. In this case particular attention should be brought to bring proper separation of concerns inside the same assembly

Continue reading →

Playing with FindFirstFile and FindNextFile

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.NET C#

Enumerating files in .NET is easy. Everybody knows the GetFiles method and you may be tempted to write code like this :

var files = Directory.GetFiles(@"c:\windows\system32", "*.dll");
    foreach (var file in files)
    {
        Console.WriteLine(file);
    }

But if you look closer you will notice that this method returns an array of strings. This could be problematic if the directory you search contains lots of files. The method will block until it performs the search and once it finishes it will load all the results into memory. It would be much better if it just returned an IEnumerable. That’s exactly what the EnumerateFiles method does in .NET 4.0. Unfortunately in .NET 3.5 there’s nothing for the job.

In this post I will show how to implement this functionality using the FindFirstFile and FindNextFile functions. Continue reading →

Fun with matrix multiplication and unsafe code

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.NET C#

In this post I will compare two methods that perform matrix multiplication. We start by defining the Matrix class:

class Matrix
    {
        private readonly double[,] _matrix;
        public Matrix(int dim1, int dim2)
        {
            _matrix = new double[dim1, dim2];
        }

        public int Height { get { return _matrix.GetLength(0); } }
        public int Width { get { return _matrix.GetLength(1); } }

        public double this[int x, int y]
        {
            get { return _matrix[x, y]; }
            set { _matrix[x, y] = value; }
        }
    }

Next we add the first algorithm to the Matrix class which performs a naive multiplication:

 public static Matrix NaiveMultiplication(Matrix m1, Matrix m2)
    {
        Matrix resultMatrix = new Matrix(m1.Height, m2.Width);
        for (int i = 0; i < resultMatrix.Height; i++)
        {
            for (int j = 0; j < resultMatrix.Width; j++)
            {
                resultMatrix[i, j] = 0;
                for (int k = 0; k < m1.Width; k++)
                {
                    resultMatrix[i, j] += m1[i, k] * m2[k, j];
                }
            }
        }
        return resultMatrix;
    }

The second method uses unsafe code: Continue reading →