private void Form1_Load(object sender,EventArgs e)
{
  MyClass my = new MyClass(); my.Name="Frank"; my.Alter=43;
  PropertyInfo[] ps = my.GetType().GetProperties();
  foreach (PropertyInfo pi in ps)
  {
    object[] atts = pi.GetCustomAttributes(typeof(SaschaAttribute),true);
    if (atts.Length > 0) MessageBox.Show("Eigenschaft <" + pi.Name + "> hat " +
      "ein Sascha Attribut");
  }
}

[AttributeUsage(AttributeTargets.Property)]
public class SaschaAttribute : Attribute
{
}

class MyClass
{
  string name;
  [Sascha]
  public string Name
  {
    get { return name; }
    set { name = value; }
  }

  int alter;
  public int Alter
  {
    get { return alter; }
    set { alter = value; }
  }
}