Descobri uma forma de fazer no form, a saber:
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Como posso arredondar apenas as bordas do Form?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
namespace teste
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public void ArredondaCantosdoForm()
{
GraphicsPath PastaGrafica = new GraphicsPath();
PastaGrafica.AddRectangle(new System.Drawing.Rectangle(1, 1, this.Size.Width, this.Size.Height));
//Arredondar canto superior esquerdo
PastaGrafica.AddRectangle(new System.Drawing.Rectangle(1, 1, 10, 10));
PastaGrafica.AddPie(1, 1, 20, 20, 180, 90);
//Arredondar canto superior direito
PastaGrafica.AddRectangle(new System.Drawing.Rectangle(this.Width - 12, 1, 12, 13));
PastaGrafica.AddPie(this.Width - 24, 1, 24, 26, 270, 90);
//Arredondar canto inferior esquerdo
PastaGrafica.AddRectangle(new System.Drawing.Rectangle(1, this.Height - 10, 10, 10));
PastaGrafica.AddPie(1, this.Height - 20, 20, 20, 90, 90);
//Arredondar canto inferior direito
PastaGrafica.AddRectangle(new System.Drawing.Rectangle(this.Width - 12, this.Height - 13, 13, 13));
PastaGrafica.AddPie(this.Width - 24, this.Height - 26, 24, 26, 0, 90);
PastaGrafica.SetMarkers();
this.Region = new Region(PastaGrafica);
}
private void Form1_Load(object sender, EventArgs e)
{
ArredondaCantosdoForm();
}
}
}
https://www.devmedia.com.br/forum/como-posso-arredondar-apenas-as-bordas-do-form/198071
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Tente adaptar para o TabPage...
[]'s,
Fabio I.