C#

public class MyChildForm : Form
{
  protected void ShowParentFormsProperty()
  {
    FormParent form = (FormParent)MdiParent;
    if (form != null) MessageBox.Show(form.MyProperty);
  }
}

public class MyChildForm : Form
{
  private FormParent parent;
  public MyChildForm(FormParent parent)
  {
    this.parent = parent; // use "this" when field and parameter are the same.
  }
  protected void ShowParentFormsProperty()
  {
    if (parent != null) MessageBox.Show(parent.MyProperty);
  }
}

public class FormParent : Form
{
  public FormParent()
  {
    // If you want to pass the parent in the constructor...
    MyChildForm form = new MyChildForm(this);
    AddOwnedForm(form);
  }
}

object value = reg.GetValue("SomeName");
if (value is string)
{
}
else if (value.GetType() == typeof(int))
{
}
else if (value.GetType() == typeof(long))
{
}
else if (value is Array)
{
}
else throw new InvalidOperationException("Unknown registry key type.");

// str is string
ldloc.0 // location of str in local variable stack
isinst [mscorlib]System.String
 
// str.GetType() == typeof(string)
ldloc.0
callvirt instance class [mscorlib]System.Type [mscorlib]System.Object::GetType()
ldtoken [mscorlib]System.String
call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(
  valuetype [mscorlib]System.RuntimeHandle)