C#

namespace MyApplication
{
	[SecurityRole("MyAppClients")]
	public interface IMyInterface
	{
		string MyMethod(string s1, string s2);
	}

	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	[ConstructionEnabled(true, Default="Server=(local);trusted connection=yes")]
	[Transaction(TransactionOption.Supported)]
	[ComponentAccessControl(true)]
	[SecurityRole("MyAppClients")]
	//[SecureMethod]
	public class MyClass: ServicedComponent, IMyInterface
	{
		private string connectionString = String.Empty;

		public MyClass()
		{
			//
			// TODO: Add constructor logic here
			//
		}
	
		protected override void Construct(string s)
		{
			this.connectionString = s;

			base.Construct(s);
		}
	
		#region IMyInterfaceimplementation

		public string MyMethod(string s1, string s2)
		{
			// TODO:  Add DataAccess.GetLogonToken implementation
			return "My String";
		}

		#endregion
	}

IMyInterface myInterface = new MyClass();

string aString = myInterface.MyMethod("s1", "s2"));

IMyInterface myInterface = new MyClass();
if(myInterface != null)
   string aString = myInterface.MyMethod("s1", "s2");

public class NumericTextBox : TextBox
{
  // ...
  protected override void OnKeyPress(KeyEventArgs e)
  {
    if (e.KeyCode < Keys.D0 || e.KeyCode > D9 ||
        e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
      e.Handled = true;

    base.OnKeyPress(e);
  }
}