Private Sub button1_Click(sender As Object, e As System.EventArgs)
    If textBox1.Text = "" Then
        MessageBox.Show("You must enter a name.", "Name Entry Error", _
           MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    Else
        ' Code to act on the data entered would go here.
    End If
End Sub

private void button1_Click(object sender, System.EventArgs e) {
   if(textBox1.Text == "") {
      MessageBox.Show("You must enter a name.", "Name Entry Error",
         MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
   }
   else {
      // Code to act on the data entered would go here.
   }
}

private:
   void button1_Click( Object^ sender, System::EventArgs^ e )
   {
      if ( textBox1->Text->Equals( "" ) )
      {
         MessageBox::Show( "You must enter a name.", "Name Entry Error",
            MessageBoxButtons::OK, MessageBoxIcon::Exclamation );
      }
      else
      {
         // Code to act on the data entered would go here.
      }
   }

Private Sub ValidateUserEntry()

    ' Checks the value of the text.

    If ServerName.Text.Length = 0 Then

        ' Initializes variables to pass to the MessageBox.Show method.

        Dim Message As String = "You did not enter a server name. Cancel this operation?"
        Dim Caption As String = "Error Detected in Input"
        Dim Buttons As MessageBoxButtons = MessageBoxButtons.YesNo

        Dim Result As DialogResult

        'Displays the MessageBox

        Result = MessageBox.Show(Message, Caption, Buttons)

        ' Gets the result of the MessageBox display.

        If Result = System.Windows.Forms.DialogResult.Yes Then

            ' Closes the parent form.

            Me.Close()

        End If

    End If

End Sub

    private void validateUserEntry()
    {

        // Checks the value of the text.

        if(serverName.Text.Length == 0)
        {

            // Initializes the variables to pass to the MessageBox.Show method.

            string message = "You did not enter a server name. Cancel this operation?";
                        string caption = "Error Detected in Input";
            MessageBoxButtons buttons = MessageBoxButtons.YesNo;
            DialogResult result;

            // Displays the MessageBox.

            result = MessageBox.Show(message, caption, buttons);

            if (result == System.Windows.Forms.DialogResult.Yes)
            {

                // Closes the parent form.

                this.Close();

            }

        }

    }

private:
   void validateUserEntry()
   {
      // Checks the value of the text.
      if ( serverName->Text->Length == 0 )
      {
         // Initializes the variables to pass to the MessageBox::Show method.
         String^ message = "You did not enter a server name. Cancel this operation?";
         String^ caption = "No Server Name Specified";
         MessageBoxButtons buttons = MessageBoxButtons::YesNo;
         System::Windows::Forms::DialogResult result;

         // Displays the MessageBox.
         result = MessageBox::Show( this, message, caption, buttons );
         if ( result == ::DialogResult::Yes )
         {
            // Closes the parent form.
            this->Close();
         }
      }
   }