Help with Paint Method

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C#

I am making an application in C # using Windows Form and I use an UserControl to draw a 3D graph. I use the Paint method to call the routines that draw the graph. First I call a routine that creates several GraphicsPath with the points the graph, then I call a routine that fills these GraphicsPath with differents tones giving the impression of 3D.

But when I minimize the application the areas that were filled loose fill and when I minimize again the fill back . How do I not miss the fill of graph each new called the Paint method. Below I put a part of my code if anyone can help me I thank you.

Paint method of the UserControl

private void wucGraficoBarras3D_Paint(object sender, PaintEventArgs e)
        {          
            oCriarGrafico.OGrafico = e.Graphics; 

            oCriarGrafico.CriarCaminhosEstrutura();

            oCriarGrafico.PreencherEstrutura();
}

Method that creates GraphicsPath with points

 public void CriarCaminhosEstrutura()
        {          
       	    PointF[] pontosBaseS = {new PointF(0.00f, 0.00f), new PointF(14.14f, -14.14f),
            new PointF(294.14f, -14.14f), new PointF(280.00f, 0.00f)};
           
            GraphicsPath caminhoBaseF = new GraphicsPath();

            oGrafico.TranslateTransform(origemX, origemY); 
         
            caminhoBaseF.AddLines(pontosBaseF);  
            caminhoBaseF.CloseFigure();
}

Method that fills the GraphicsPath with various shades

public void PreencherEstrutura()
        {
            mistura.Factors = fatoresBlend;
            mistura.Positions = posicoesBlend;
           
            pontoInicialEstruturaBlend = new PointF(0.00f, 4.00f);
            pontoFinalEstruturaBlend = new PointF(280.00f, 4.00f);
            corEstrutura1 = Color.FromArgb(255, Color.DarkGray);
            corEstrutura2 = Color.FromArgb(255, Color.Gray);
            LinearGradientBrush escovaEstrutura = new LinearGradientBrush(pontoInicialEstruturaBlend,
                pontoFinalEstruturaBlend, corEstrutura1, corEstrutura2);
            escovaEstrutura.Blend = mistura;
            oGrafico.FillPath(escovaEstrutura, caminhoBaseF);
}