C#

namespace CustomControls
{
    public enum NumModel
    {
        /// <summary>
        /// 
        /// </summary>
        PositiveInteger,
        /// <summary>
        /// 
        /// </summary>
        PositiveFloat
    }
    public class NumberTextBox : TextBox
    {
        private NumModel numModel = NumModel.PositiveInteger;
        /// <summary>
        /// 
        /// </summary>
        public NumModel NumModel
        {
            get
            {
                return numModel;
            }
            set
            {
                numModel = value;
            }
        }

        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            if ((e.KeyChar >= '0' && e.KeyChar <= '9') || (e.KeyChar == 8) || (e.KeyChar == 46))
            {
                if (numModel == NumModel.PositiveInteger)
                {
                    if ((e.KeyChar == 46))
                    {
                        e.Handled = true;
                    }
                    else
                    {
                        e.Handled = false;
                        //base.OnKeyPress(e);
                    }
                }
                else
                {
                    if ((this.Text.Contains(".") && (e.KeyChar == 46)))
                    {
                        e.Handled = true;
                    }
                    else
                    {
                        e.Handled = false;
                        // base.OnKeyPress(e);
                    }
                }
            }
            else
            {

                e.Handled = true;
            }
        }
        protected override void OnKeyUp(KeyEventArgs e)
        {
            double num;
            if (this.Text != null && this.Text != "" && !double.TryParse(this.Text, out num))
            {
                //SendKeys.Send("{Backspace}");
                this.Text = this.Text.Substring(0, this.Text.Length - 1);
                this.Select(this.Text.Length, 0);
            }
            base.OnKeyUp(e);
        }
    }
}

class MyClass
   {
   public int Value {get; set;}
   public MyClass(int x) { Value = x;}
   }
MyClass[] data = new MyClass[2];
MyClass x = new MyClass(333);
MyClass y = new MyClass(666);
myClass z = new MyClass(999);
myClass[0] = x;
myClass[1] = y;
myClass[0] = z;
myClass[1].Value = 111;

this.CurrentUser.Companies[idx] = comp;

this.CurrentUser.Companies[idx].BusinessName = comp.BusinessName;

/// <summary>
/// Gets the assembly Title
/// </summary>
public string AssemblyTitle
    {
    get
        {
        object[] attributes = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(AssemblyTitleAttribute), false);
        if (attributes.Length > 0)
            {
            AssemblyTitleAttribute titleAttribute = (AssemblyTitleAttribute)attributes[0];
            if (titleAttribute.Title != "")
                {
                return titleAttribute.Title;
                }
            }
        return System.IO.Path.GetFileNameWithoutExtension(Assembly.GetExecutingAssembly().CodeBase);
        }
    }
/// <summary>
/// Gets the assembly Version
/// </summary>
public string AssemblyVersion
    {
    get
        {
        return Assembly.GetExecutingAssembly().GetName().Version.ToString();
        }
    }
/// <summary>
/// Gets the assembly Description
/// </summary>
public string AssemblyDescription
    {
    get
        {
        object[] attributes = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(AssemblyDescriptionAttribute), false);
        if (attributes.Length == 0)
            {
            return "";
            }
        return ((AssemblyDescriptionAttribute)attributes[0]).Description;
        }
    }
/// <summary>
/// Gets the assembly Product
/// </summary>
public string AssemblyProduct
    {
    get
        {
        object[] attributes = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(AssemblyProductAttribute), false);
        if (attributes.Length == 0)
            {
            return "";
            }
        return ((AssemblyProductAttribute)attributes[0]).Product;
        }
    }
/// <summary>
/// Gets the assembly copyright notice
/// </summary>
public string AssemblyCopyright
    {
    get
        {
        object[] attributes = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(AssemblyCopyrightAttribute), false);
        if (attributes.Length == 0)
            {
            return "";
            }
        return ((AssemblyCopyrightAttribute)attributes[0]).Copyright;
        }
    }
/// <summary>
/// Gets the assembly Company
/// </summary>
public string AssemblyCompany
    {
    get
        {
        object[] attributes = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(AssemblyCompanyAttribute), false);
        if (attributes.Length == 0)
            {
            return "";
            }
        return ((AssemblyCompanyAttribute)attributes[0]).Company;
        }
    }

thx.
the application is a banking app.
it will deal with:account, customers, transactions and other 
banking products.
I agree with Gerry Schmitz. I started with DFD and the business logic.
As I said before, I will perform a reading from different 
types of data sources(db and file system) this is my app domain.
And for business domain: banking rules, control, security, continuity.
infrastructure:
- repository pattern (EF dbcontext) and uow
- repository for file system (helper parsers )
- repository for Web Services 

web services and file system having the same output/input business logic.
DB for saving and checking.

Finally to enssure the continuity we have to process the older (File system) and the newer
data sources (Web service)